[InstCombine] Baseline test exposing vector fp-to-int conversion becoming scalar (llvm#165800)

Baseline test for llvm#165793
exposing the change from a vector fp-to-int conversion into a scalar one
inside the loop.

Additionally, removed
`llvm/test/Transforms/InstCombine/vec_extract_var_elt-inseltpoison.ll`,
which was a duplicate of
`llvm/test/Transforms/InstCombine/vec_extract_var_elt.ll` differing only
by the use of poison in the insert element.
The poison variant has been merged into
`llvm/test/Transforms/InstCombine/vec_extract_var_elt.ll`.

Also improved test naming and updated test checks.

Author: azwolski

llvm/test/Transforms/InstCombine/vec_extract_var_elt-inseltpoison.ll

@@ -1,26 +1,81 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
 ; RUN: opt < %s -passes=instcombine -S | FileCheck %s
 
-define void @test (float %b, ptr %p)  {
-; CHECK: extractelement
-; CHECK: fptosi
-  %1 = load <8 x float> , ptr %p
+define void @test_poison(float %b, ptr %p) {
+; CHECK-LABEL: define void @test_poison(
+; CHECK-SAME: float [[B:%.*]], ptr [[P:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = load <8 x float>, ptr [[P]], align 32
+; CHECK-NEXT:    [[TMP2:%.*]] = fptosi float [[B]] to i32
+; CHECK-NEXT:    [[TMP3:%.*]] = add i32 [[TMP2]], -2
+; CHECK-NEXT:    [[TMP4:%.*]] = extractelement <8 x float> [[TMP1]], i32 [[TMP3]]
+; CHECK-NEXT:    [[TMP5:%.*]] = fptosi float [[TMP4]] to i32
+; CHECK-NEXT:    [[TMP6:%.*]] = insertelement <8 x i32> poison, i32 [[TMP5]], i64 7
+; CHECK-NEXT:    [[TMP7:%.*]] = sitofp <8 x i32> [[TMP6]] to <8 x float>
+; CHECK-NEXT:    store <8 x float> [[TMP7]], ptr [[P]], align 32
+; CHECK-NEXT:    ret void
+;
+  %1 = load <8 x float>, ptr %p
   %2 = bitcast <8 x float> %1 to <8 x i32>
   %3 = bitcast <8 x i32> %2 to <8 x float>
   %a = fptosi <8 x float> %3 to <8 x i32>
   %4 = fptosi float %b to i32
   %5 = add i32 %4, -2
   %6 = extractelement <8 x i32> %a, i32 %5
-  %7 = insertelement <8 x i32> undef, i32 %6, i32 7
+  %7 = insertelement <8 x i32> poison, i32 %6, i32 7
   %8 = sitofp <8 x i32> %7 to <8 x float>
   store <8 x float> %8, ptr %p
-  ret void    
+  ret void
 }
 
 ; PR18600
-define i32 @test2(i32 %i) {
+define i32 @test_bitcast(i32 %i) {
+; CHECK-LABEL: define i32 @test_bitcast(
+; CHECK-SAME: i32 [[I:%.*]]) {
+; CHECK-NEXT:    [[E:%.*]] = extractelement <4 x i32> <i32 1, i32 0, i32 2, i32 0>, i32 [[I]]
+; CHECK-NEXT:    ret i32 [[E]]
+;
   %e = extractelement <4 x i32> bitcast (<2 x i64> <i64 1, i64 2> to <4 x i32>), i32 %i
   ret i32 %e
+}
+
+declare void @use(i32)
 
-; CHECK-LABEL: @test2
-; CHECK: extractelement
+define void @test_loop(<4 x float> %in) {
+; CHECK-LABEL: define void @test_loop(
+; CHECK-SAME: <4 x float> [[IN:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    [[R:%.*]] = call <4 x float> @llvm.x86.sse41.round.ps(<4 x float> [[IN]], i32 9)
+; CHECK-NEXT:    br label %[[LOOP:.*]]
+; CHECK:       [[LOOP]]:
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ [[NEXT:%.*]], %[[LATCH:.*]] ]
+; CHECK-NEXT:    [[COND:%.*]] = icmp samesign ult i32 [[I]], 4
+; CHECK-NEXT:    br i1 [[COND]], label %[[BODY:.*]], label %[[DONE:.*]]
+; CHECK:       [[BODY]]:
+; CHECK-NEXT:    [[TMP0:%.*]] = extractelement <4 x float> [[R]], i32 [[I]]
+; CHECK-NEXT:    [[ELEM:%.*]] = fptosi float [[TMP0]] to i32
+; CHECK-NEXT:    call void @use(i32 [[ELEM]])
+; CHECK-NEXT:    br label %[[LATCH]]
+; CHECK:       [[LATCH]]:
+; CHECK-NEXT:    [[NEXT]] = add nuw nsw i32 [[I]], 1
+; CHECK-NEXT:    br label %[[LOOP]]
+; CHECK:       [[DONE]]:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %r = call <4 x float> @llvm.x86.sse41.round.ps(<4 x float> %in, i32 9)
+  %vi = fptosi <4 x float> %r to <4 x i32>
+  br label %loop
+loop:
+  %i = phi i32 [ 0, %entry ], [ %next, %latch ]
+  %cond = icmp ult i32 %i, 4
+  br i1 %cond, label %body, label %done
+body:
+  %elem = extractelement <4 x i32> %vi, i32 %i
+  call void @use(i32 %elem)
+  br label %latch
+latch:
+  %next = add i32 %i, 1
+  br label %loop
+done:
+  ret void
 }