[llvm] [InstCombine] Fold `fpto{s|u}i non-norm` to zero (PR #85569)

[Matt Arsenault via llvm-commits]

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@@ -347,3 +347,64 @@ define double @masked_uint_to_fpext3(i32 %x) {
   %r = fpext float %f to double
   ret double %r
 }
+
+define i32 @fptosi_nonnorm(float nofpclass(norm) %x) {
+; CHECK-LABEL: @fptosi_nonnorm(
+; CHECK-NEXT:    ret i32 0
+;
+  %ret = fptosi float %x to i32
+  ret i32 %ret
+}
+
+define i32 @fptoui_nonnorm(float nofpclass(pnorm) %x) {
+; CHECK-LABEL: @fptoui_nonnorm(
+; CHECK-NEXT:    ret i32 0
+;
+  %ret = fptoui float %x to i32
+  ret i32 %ret
+}
+
+define i32 @fptosi_nonnorm_copysign(float %x) {
+; CHECK-LABEL: @fptosi_nonnorm_copysign(
+; CHECK-NEXT:    ret i32 0
+;
+  %val = call float @llvm.copysign.f32(float 0.0, float %x)
+  %ret = fptosi float %val to i32
+  ret i32 %ret
+}
+
+define i32 @fptosi_nonnorm_fmul(float %x) {
+; CHECK-LABEL: @fptosi_nonnorm_fmul(
+; CHECK-NEXT:    [[SEL:%.*]] = fmul float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    [[RET:%.*]] = fptosi float [[SEL]] to i32
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %sel = fmul float %x, 0.000000e+00
+  %ret = fptosi float %sel to i32
+  ret i32 %ret
+}
+
+define i32 @fptosi_select(i1 %cond) {
+; CHECK-LABEL: @fptosi_select(
+; CHECK-NEXT:    [[RET:%.*]] = select i1 [[COND:%.*]], i32 1, i32 -1
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  %sel = select i1 %cond, float 1.0, float -1.0
+  %ret = fptosi float %sel to i32
+  ret i32 %ret
+}
+
+define i32 @mul_pos_zero_convert(i32 %a) {
+; CHECK-LABEL: @mul_pos_zero_convert(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[FP:%.*]] = sitofp i32 [[A:%.*]] to float
+; CHECK-NEXT:    [[RET:%.*]] = fmul float [[FP]], 0.000000e+00
+; CHECK-NEXT:    [[CONV:%.*]] = fptosi float [[RET]] to i32
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+entry:
+  %fp = sitofp i32 %a to float
+  %ret = fmul float %fp, 0.000000e+00
+  %conv = fptosi float %ret to i32
+  ret i32 %conv
+}
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arsenm wrote:

Needs some vector tests 

https://github.com/llvm/llvm-project/pull/85569