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Add test for clamp like case where the first select is a ([s/z]ext (icmp))
This ([s/z]ext (icmp)) is equivilant to (select icmp, [1/-1], 0), so can be canonicalized too. This is generally not beneficial because after the canonicalization we lose the ability replace one of the selects with ([s/z]ext (icmp)). However, it is beneficial for this particular case: ``` %old_cmp1 = icmp sgt i32 %x, C2 %old_replacement = sext i1 %old_cmp1 to i32 %old_cmp0 = icmp ult i32 %x, C0 %r = select i1 %old_cmp0, i32 %x, i32 %old_replacement it can be rewriten as more canonical pattern: %new_cmp2 = icmp sge i32 %x, C0 %new_clamped_low = smax i32 %target_low, i32 %x %r = select i1 %new_cmp2, i32 -1, i32 %new_clamped_low Iff 0 s<= C2 s<= C0 ``` The select can be lowered to: ``` %sext_cmp2 = sext i1 %new_cmp2 to i32 %r = or i32 %sext_cmp2, i32 %new_clamped_low ```
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‎llvm/test/Transforms/InstCombine/canonicalize-clamp-like-pattern-i1.ll‎

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -passes='instcombine<no-verify-fixpoint>' -S | FileCheck %s
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; Given a pattern like:
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; %old_cmp1 = icmp sgt i32 %x, C2
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; %old_replacement = sext i1 %old_cmp1 to i32
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; %old_cmp0 = icmp ult i32 %x, C0
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; %r = select i1 %old_cmp0, i32 %x, i32 %old_replacement
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; it can be rewriten as more canonical pattern:
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; %new_cmp2 = icmp sge i32 %x, C0
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; %new_clamped_low = smax i32 %target_low, i32 %x
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; %r = select i1 %new_cmp2, i32 -1, i32 %new_clamped_low
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; Iff 0 s<= C2 s<= C0
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; Also, ULT predicate can also be UGE; or UGT iff C0 != -1 (+invert result)
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; Also, SLT predicate can also be SGE; or SGT iff C2 != INT_MAX (+invert res.)
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;-------------------------------------------------------------------------------
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; clamp-like max case, can be optimized with max
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define i32 @clamp_max_sgt(i32 %x) {
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; CHECK-LABEL: @clamp_max_sgt(
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 256
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; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], 0
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; CHECK-NEXT: [[COND:%.*]] = sext i1 [[CMP2]] to i32
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; CHECK-NEXT: [[COND3:%.*]] = select i1 [[OR_COND]], i32 [[X]], i32 [[COND]]
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; CHECK-NEXT: ret i32 [[COND3]]
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;
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%or.cond = icmp ult i32 %x, 256
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%cmp2 = icmp sgt i32 %x, 0
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%cond = sext i1 %cmp2 to i32
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%cond3 = select i1 %or.cond, i32 %x, i32 %cond
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ret i32 %cond3
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}
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; clamp-like max case with vector, can be optimized with max
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define <2 x i32> @clamp_max_sgt_vec(<2 x i32> %x) {
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; CHECK-LABEL: @clamp_max_sgt_vec(
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult <2 x i32> [[X:%.*]], <i32 100, i32 256>
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; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt <2 x i32> [[X]], <i32 98, i32 254>
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; CHECK-NEXT: [[COND:%.*]] = sext <2 x i1> [[CMP2]] to <2 x i32>
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; CHECK-NEXT: [[COND3:%.*]] = select <2 x i1> [[OR_COND]], <2 x i32> [[X]], <2 x i32> [[COND]]
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; CHECK-NEXT: ret <2 x i32> [[COND3]]
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;
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%or.cond = icmp ult <2 x i32> %x, <i32 100, i32 256>
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%cmp2 = icmp sgt <2 x i32> %x, <i32 98, i32 254>
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%cond = sext <2 x i1> %cmp2 to <2 x i32>
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%cond3 = select <2 x i1> %or.cond, <2 x i32> %x, <2 x i32> %cond
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ret <2 x i32> %cond3
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}
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; Not clamp-like vector
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define <2 x i32> @clamp_max_vec(<2 x i32> %x) {
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; CHECK-LABEL: @clamp_max_vec(
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult <2 x i32> [[X:%.*]], <i32 100, i32 256>
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; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt <2 x i32> [[X]], <i32 128, i32 0>
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; CHECK-NEXT: [[COND:%.*]] = sext <2 x i1> [[CMP2]] to <2 x i32>
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; CHECK-NEXT: [[COND3:%.*]] = select <2 x i1> [[OR_COND]], <2 x i32> [[X]], <2 x i32> [[COND]]
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; CHECK-NEXT: ret <2 x i32> [[COND3]]
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;
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%or.cond = icmp ult <2 x i32> %x, <i32 100, i32 256>
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%cmp2 = icmp sgt <2 x i32> %x, <i32 128, i32 0>
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%cond = sext <2 x i1> %cmp2 to <2 x i32>
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%cond3 = select <2 x i1> %or.cond, <2 x i32> %x, <2 x i32> %cond
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ret <2 x i32> %cond3
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}
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; clamp-like max case, can be optimized with max
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define i32 @clamp_max_sgt_neg1(i32 %x) {
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; CHECK-LABEL: @clamp_max_sgt_neg1(
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 256
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; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], -1
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; CHECK-NEXT: [[COND:%.*]] = sext i1 [[CMP2]] to i32
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; CHECK-NEXT: [[COND3:%.*]] = select i1 [[OR_COND]], i32 [[X]], i32 [[COND]]
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; CHECK-NEXT: ret i32 [[COND3]]
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;
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%or.cond = icmp ult i32 %x, 256
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%cmp2 = icmp sgt i32 %x, -1
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%cond = sext i1 %cmp2 to i32
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%cond3 = select i1 %or.cond, i32 %x, i32 %cond
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ret i32 %cond3
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}
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; clamp-like max case, can be optimized with max
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define i32 @clamp_max_sge(i32 %x) {
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; CHECK-LABEL: @clamp_max_sge(
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 256
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; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], -1
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; CHECK-NEXT: [[COND:%.*]] = sext i1 [[CMP2]] to i32
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; CHECK-NEXT: [[COND3:%.*]] = select i1 [[OR_COND]], i32 [[X]], i32 [[COND]]
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; CHECK-NEXT: ret i32 [[COND3]]
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;
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%or.cond = icmp ult i32 %x, 256
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%cmp2 = icmp sge i32 %x, 0
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%cond = sext i1 %cmp2 to i32
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%cond3 = select i1 %or.cond, i32 %x, i32 %cond
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ret i32 %cond3
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}
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; Don't support SLT cases, need to select 0 as the low value, -1 as high value
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define i32 @clamp_max_slt(i32 %x) {
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; CHECK-LABEL: @clamp_max_slt(
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 256
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; CHECK-NEXT: [[COND:%.*]] = ashr i32 [[X]], 31
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; CHECK-NEXT: [[COND3:%.*]] = select i1 [[OR_COND]], i32 [[X]], i32 [[COND]]
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; CHECK-NEXT: ret i32 [[COND3]]
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;
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%or.cond = icmp ult i32 %x, 256
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%cmp2 = icmp slt i32 %x, 0
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%cond = sext i1 %cmp2 to i32
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%cond3 = select i1 %or.cond, i32 %x, i32 %cond
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ret i32 %cond3
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}
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; Don't support SLE cases, need to select 0 as the low value, -1 as high value
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define i32 @clamp_max_sle(i32 %x) {
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; CHECK-LABEL: @clamp_max_sle(
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 256
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; CHECK-NEXT: [[CMP2:%.*]] = icmp slt i32 [[X]], 1
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; CHECK-NEXT: [[COND:%.*]] = sext i1 [[CMP2]] to i32
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; CHECK-NEXT: [[COND3:%.*]] = select i1 [[OR_COND]], i32 [[X]], i32 [[COND]]
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; CHECK-NEXT: ret i32 [[COND3]]
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;
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%or.cond = icmp ult i32 %x, 256
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%cmp2 = icmp sle i32 %x, 0
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%cond = sext i1 %cmp2 to i32
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%cond3 = select i1 %or.cond, i32 %x, i32 %cond
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ret i32 %cond3
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}
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; Not selecting between 0, x, and -1, so can't be optimized with max
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; Select between 0, x, and 1
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define i32 @clamp_max_bad_values(i32 %x) {
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; CHECK-LABEL: @clamp_max_bad_values(
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[X:%.*]], 256
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; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], 0
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; CHECK-NEXT: [[COND:%.*]] = zext i1 [[CMP2]] to i32
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; CHECK-NEXT: [[COND3:%.*]] = select i1 [[OR_COND]], i32 [[X]], i32 [[COND]]
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; CHECK-NEXT: ret i32 [[COND3]]
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;
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%or.cond = icmp ult i32 %x, 256
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%cmp2 = icmp sgt i32 %x, 0
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%cond = zext i1 %cmp2 to i32
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%cond3 = select i1 %or.cond, i32 %x, i32 %cond
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ret i32 %cond3
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}
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; Boundaries of range are not 0 and x (x is some positive integer)
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define i32 @clamp_max_offset(i32 %x) {
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; CHECK-LABEL: @clamp_max_offset(
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; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[X:%.*]], -10
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; CHECK-NEXT: [[OR_COND:%.*]] = icmp ult i32 [[TMP1]], 246
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; CHECK-NEXT: [[CMP2:%.*]] = icmp sgt i32 [[X]], 10
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; CHECK-NEXT: [[COND:%.*]] = sext i1 [[CMP2]] to i32
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; CHECK-NEXT: [[COND3:%.*]] = select i1 [[OR_COND]], i32 [[X]], i32 [[COND]]
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; CHECK-NEXT: ret i32 [[COND3]]
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;
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%1 = add i32 %x, -10
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%or.cond = icmp ult i32 %1, 246
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%cmp2 = icmp sgt i32 %x, 10
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%cond = sext i1 %cmp2 to i32
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%cond3 = select i1 %or.cond, i32 %x, i32 %cond
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ret i32 %cond3
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}

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