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llvm-reduce: Add pass to sink defs to uses (#170317)
The intent is to reduce live ranges and reduce the impact on later scheduling on the testcase.
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‎llvm/test/tools/llvm-reduce/reduce-sink-defs-to-uses.ll‎

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; Test that llvm-reduce can move def instructions down to uses.
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;
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; RUN: llvm-reduce --abort-on-invalid-reduction --delta-passes=sink-defs-to-uses --test FileCheck --test-arg --check-prefixes=CHECK,INTERESTING --test-arg %s --test-arg --input-file %s -o %t
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; RUN: FileCheck --check-prefixes=CHECK,RESULT %s < %t
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declare i32 @leaf()
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declare void @func()
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declare void @use(i32)
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declare void @use0(i32)
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declare void @use1(i32)
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declare void @use2(i32)
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declare i32 @leaf_with_arg(i32)
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; CHECK-LABEL: define i32 @sink_leaf_to_ret() {
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; INTERESTING: call i32 @leaf()
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; RESULT-NEXT: call void @func()
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; RESULT-NEXT: %ret = call i32 @leaf()
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; RESULT-NEXT: ret i32 %ret
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define i32 @sink_leaf_to_ret() {
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%ret = call i32 @leaf()
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call void @func()
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ret i32 %ret
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}
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; CHECK-LABEL: define i32 @no_sink_leaf_to_ret() {
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; INTERESTING: call i32 @leaf()
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; INTERESTING: call void @func()
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; RESULT: %ret = call i32 @leaf()
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; RESULT-NEXT: call void @func()
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; RESULT-NEXT: ret i32 %ret
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define i32 @no_sink_leaf_to_ret() {
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%ret = call i32 @leaf()
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call void @func()
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ret i32 %ret
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}
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; CHECK-LABEL: define i32 @sink_across_trivial_block() {
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; RESULT: {{^}}entry:
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; RESULT-NEXT: br label %ret
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; RESULT: {{^}}ret:
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; RESULT-NEXT: call void @func
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; RESULT-NEXT: %val = call i32 @leaf()
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; RESULT-NEXT: ret i32 %val
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define i32 @sink_across_trivial_block() {
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entry:
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%val = call i32 @leaf()
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br label %ret
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ret:
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call void @func()
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ret i32 %val
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}
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; CHECK-LABEL: define i32 @cannot_sink_phi_def(
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; INTERESTING: phi i32
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; RESULT: {{^}}b:
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; RESULT-NEXT: %phi = phi i32
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; RESULT-NEXT: call void @func(
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; RESULT-NEXT: ret i32 %phi
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define i32 @cannot_sink_phi_def(i1 %cond) {
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entry:
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br i1 %cond, label %a, label %b
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a:
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br label %b
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b:
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%phi = phi i32 [ 0, %entry ], [ 1, %a ]
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call void @func()
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ret i32 %phi
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}
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; CHECK-LABEL: define i32 @cannot_sink_phi_use(
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; INTERESTING: phi i32
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define i32 @cannot_sink_phi_use(ptr %arg) {
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entry:
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call void @func()
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br label %loop
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loop:
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%phi = phi i32 [ 0, %entry ], [ %add, %loop ]
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call void @func()
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%def0 = call i32 @leaf()
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call void @func()
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%add = add i32 %phi, 1
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%loop.cond = load volatile i1, ptr %arg
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br i1 %loop.cond, label %loop, label %exit
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exit:
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ret i32 %phi
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}
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; CHECK-LABEL: define i32 @cannot_sink_past_other_use(
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; INTERESTING: call i32 @leaf
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; RESULT-NEXT: %val = call i32
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; RESULT-NEXT: call void @use(i32 %val)
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; RESULT-NEXT: ret i32 %val
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define i32 @cannot_sink_past_other_use() {
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%val = call i32 @leaf()
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call void @use(i32 %val)
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ret i32 %val
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}
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; CHECK-LABEL: define void @no_sink_alloca(
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; CHECK-NEXT: alloca
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; RESULT-NEXT: call void @func
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; RESULT-NEXT: store i32
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; RESULT-NEXT: ret
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define void @no_sink_alloca() {
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%alloca = alloca i32
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call void @func()
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store i32 0, ptr %alloca
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ret void
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}
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; CHECK-LABEL: define i32 @cannot_sink_callbr(
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; CHECK: callbr i32
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; RESULT: store i32 1
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; RESULT-NEXT: ret i32 %load0
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; RESULT: store i32 2
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; RESULT-NEXT: ret i32 2
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; RESULT: store i32 3
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; RESULT-NEXT: ret i32 3
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define i32 @cannot_sink_callbr(ptr %arg0, ptr %ptr1) {
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entry:
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%load0 = load i32, ptr %arg0
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%callbr = callbr i32 asm "", "=r,r,!i,!i"(i32 %load0)
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to label %one [label %two, label %three]
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one:
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store i32 1, ptr %ptr1
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ret i32 %load0
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two:
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store i32 2, ptr %ptr1
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ret i32 2
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three:
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store i32 3, ptr %ptr1
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ret i32 3
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}
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declare i32 @__gxx_personality_v0(...)
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declare i32 @maybe_throwing_callee(i32)
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declare void @did_not_throw(i32)
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; landingpad must be first in the block, so it cannot be sunk.
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; CHECK-LABEL: @cannot_sink_landingpad(
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; INTERESTING: landingpad
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; RESULT: %landing = landingpad { ptr, i32 }
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; RESULT-NEXT: catch ptr
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; RESULT-NEXT: call void @func(
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; RESULT-NEXT: call void @func(
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; RESULT-NEXT: extractvalue { ptr, i32 } %landing, 1
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define void @cannot_sink_landingpad(i32 %arg) personality ptr @__gxx_personality_v0 {
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bb:
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%i0 = invoke i32 @maybe_throwing_callee(i32 %arg)
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to label %bb3 unwind label %bb1
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bb1: ; preds = %bb
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%landing = landingpad { ptr, i32 }
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catch ptr null
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call void @func()
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call void @func()
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%extract0 = extractvalue { ptr, i32 } %landing, 1
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call void @use(i32 %extract0)
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br label %bb4
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bb3: ; preds = %bb
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call void @did_not_throw(i32 %i0)
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br label %bb4
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bb4: ; preds = %bb3, %bb1
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ret void
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}
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; CHECK-LABEL: define void @sink_multiple_uses() {
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; INTERESTING: call i32 @leaf(
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; INTERESTING: call void @use0(
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; RESULT-NEXT: call void @func(
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; RESULT-NEXT: %ret = call i32 @leaf()
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; RESULT-NEXT: call void @use0(i32 %ret)
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define void @sink_multiple_uses() {
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%ret = call i32 @leaf()
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call void @func()
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call void @use0(i32 %ret)
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call void @func()
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call void @use1(i32 %ret)
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call void @func()
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call void @use2(i32 %ret)
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ret void
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}
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; CHECK-LABEL: define i32 @can_sink_end_diamond(
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; RESULT: entry:
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; RESULT-NEXT: br i1
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; RESULT: endif:
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; RESULT-NEXT: %val = call i32 @leaf()
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; RESULT-NEXT: call void @use(i32 %val)
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; RESULT-NEXT: ret i32 %val
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define i32 @can_sink_end_diamond(i1 %cond) {
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entry:
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%val = call i32 @leaf()
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br i1 %cond, label %a, label %b
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a:
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br label %endif
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b:
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br label %endif
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endif:
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call void @use(i32 %val)
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ret i32 %val
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}
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; CHECK-LABEL: define i32 @cannot_sink_diamond_end_0(
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; RESULT: entry:
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; RESULT-NEXT: %val = call i32 @leaf()
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define i32 @cannot_sink_diamond_end_0(i1 %cond) {
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entry:
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%val = call i32 @leaf()
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br i1 %cond, label %a, label %b
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a:
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call void @use0(i32 %val)
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br label %endif
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b:
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call void @use1(i32 %val)
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br label %endif
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endif:
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ret i32 %val
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}
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; CHECK-LABEL: define void @cannot_sink_diamond_end_1(
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; RESULT: entry:
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; RESULT-NEXT: %val = call i32 @leaf()
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define void @cannot_sink_diamond_end_1(i1 %cond) {
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entry:
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%val = call i32 @leaf()
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br i1 %cond, label %a, label %b
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a:
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call void @use0(i32 %val)
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br label %endif
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b:
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call void @use1(i32 %val)
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br label %endif
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endif:
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ret void
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}

‎llvm/tools/llvm-reduce/CMakeLists.txt‎

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@@ -60,6 +60,7 @@ add_llvm_tool(llvm-reduce
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deltas/ReduceRegisterMasks.cpp
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deltas/ReduceRegisterDefs.cpp
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deltas/ReduceRegisterUses.cpp
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deltas/ReduceSinkDefsToUses.cpp
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deltas/ReduceTargetFeaturesAttr.cpp
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deltas/ReduceUsingSimplifyCFG.cpp
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deltas/RunIRPasses.cpp

‎llvm/tools/llvm-reduce/DeltaManager.cpp‎

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#include "deltas/ReduceRegisterDefs.h"
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#include "deltas/ReduceRegisterMasks.h"
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#include "deltas/ReduceRegisterUses.h"
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#include "deltas/ReduceSinkDefsToUses.h"
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#include "deltas/ReduceSpecialGlobals.h"
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#include "deltas/ReduceTargetFeaturesAttr.h"
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#include "deltas/ReduceUsingSimplifyCFG.h"

‎llvm/tools/llvm-reduce/DeltaPasses.def‎

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@@ -59,6 +59,7 @@ DELTA_PASS_IR("atomic-ordering", reduceAtomicOrderingDeltaPass, "Reducing Atomic
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DELTA_PASS_IR("syncscopes", reduceAtomicSyncScopesDeltaPass, "Reducing Atomic Sync Scopes")
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DELTA_PASS_IR("instruction-flags", reduceInstructionFlagsDeltaPass, "Reducing Instruction Flags")
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DELTA_PASS_IR("inline-call-sites", reduceInlineCallSitesDeltaPass, "Inlining callsites")
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DELTA_PASS_IR("sink-defs-to-uses", reduceSinkDefsToUsesDeltaPass, "Sinking defs to uses")
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#ifndef DELTA_PASS_MIR
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#define DELTA_PASS_MIR(NAME, FUNC, DESC)

‎llvm/tools/llvm-reduce/deltas/ReduceSinkDefsToUses.cpp‎

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//===- ReduceSinkDefsToUses.cpp - Specialized Delta Pass ------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Try to move defs to be next to their uses
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//
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//===----------------------------------------------------------------------===//
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#include "ReduceSinkDefsToUses.h"
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#include "Utils.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Instructions.h"
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using namespace llvm;
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static bool shouldPreserveUsePosition(const Instruction &I) {
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return isa<AllocaInst>(I) || isa<PHINode>(I) || I.isEHPad();
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}
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static bool shouldPreserveDefPosition(const Instruction &I) {
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return shouldPreserveUsePosition(I) || I.isTerminator();
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}
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static void sinkDefsToUsesInFunction(Oracle &O, Function &F) {
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DominatorTree DT(F);
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for (BasicBlock &BB : F) {
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for (Instruction &UseInst : make_early_inc_range(reverse(BB))) {
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if (shouldPreserveUsePosition(UseInst))
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continue;
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for (Value *UseOp : UseInst.operands()) {
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Instruction *DefInst = dyn_cast<Instruction>(UseOp);
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if (!DefInst || shouldPreserveDefPosition(*DefInst))
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continue;
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if (!all_of(DefInst->users(), [&](const User *DefUser) {
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return DefUser == &UseInst ||
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DT.dominates(&UseInst, cast<Instruction>(DefUser));
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})) {
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continue;
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}
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if (!O.shouldKeep())
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DefInst->moveBeforePreserving(UseInst.getIterator());
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}
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}
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}
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}
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void llvm::reduceSinkDefsToUsesDeltaPass(Oracle &O, ReducerWorkItem &WorkItem) {
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Module &M = WorkItem.getModule();
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for (Function &F : M) {
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if (!F.isDeclaration())
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sinkDefsToUsesInFunction(O, F);
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}
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}

‎llvm/tools/llvm-reduce/deltas/ReduceSinkDefsToUses.h‎

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//===- ReduceSinkDefsToUses.h - Specialized Delta Pass ----------*- C++- *-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TOOLS_LLVM_REDUCE_DELTAS_SINKDEFSTOUSES_H
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#define LLVM_TOOLS_LLVM_REDUCE_DELTAS_SINKDEFSTOUSES_H
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#include "Delta.h"
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namespace llvm {
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void reduceSinkDefsToUsesDeltaPass(Oracle &O, ReducerWorkItem &WorkItem);
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} // namespace llvm
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#endif

‎llvm/utils/gn/secondary/llvm/tools/llvm-reduce/BUILD.gn‎

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@@ -48,6 +48,7 @@ executable("llvm-reduce") {
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"deltas/ReduceRegisterDefs.cpp",
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"deltas/ReduceRegisterMasks.cpp",
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"deltas/ReduceRegisterUses.cpp",
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"deltas/ReduceSinkDefsToUses.cpp",
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"deltas/ReduceSpecialGlobals.cpp",
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"deltas/ReduceTargetFeaturesAttr.cpp",
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"deltas/ReduceUsingSimplifyCFG.cpp",

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