[llvm] InstCombine: Try to fold ldexp with select of power operand (PR #97354)

[Yingwei Zheng via llvm-commits]

================
@@ -889,6 +889,132 @@ define float @ldexp_8_contractable(float %x, float %y) {
   ret float %fadd
 }
 
+define float @ldexp_f32_mask_select_0(i1 %cond, float %x, i32 %y) {
+; CHECK-LABEL: define float @ldexp_f32_mask_select_0
+; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call float @llvm.ldexp.f32.i32(float [[X]], i32 [[Y]])
+; CHECK-NEXT:    [[LDEXP:%.*]] = select i1 [[COND]], float [[TMP1]], float [[X]]
+; CHECK-NEXT:    ret float [[LDEXP]]
+;
+  %select = select i1 %cond, i32 %y, i32 0
+  %ldexp = call float @llvm.ldexp.f32.i32(float %x, i32 %select)
+  ret float %ldexp
+}
+
+define float @ldexp_nnan_f32_mask_select_0(i1 %cond, float %x, i32 %y) {
+; CHECK-LABEL: define float @ldexp_nnan_f32_mask_select_0
+; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan float @llvm.ldexp.f32.i32(float [[X]], i32 [[Y]])
+; CHECK-NEXT:    [[LDEXP:%.*]] = select i1 [[COND]], float [[TMP1]], float [[X]]
+; CHECK-NEXT:    ret float [[LDEXP]]
+;
+  %select = select i1 %cond, i32 %y, i32 0
+  %ldexp = call nnan float @llvm.ldexp.f32.i32(float %x, i32 %select)
+  ret float %ldexp
+}
+
+define float @ldexp_flags_f32_mask_select_0(i1 %cond, float %x, i32 %y) {
+; CHECK-LABEL: define float @ldexp_flags_f32_mask_select_0
+; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call ninf nsz float @llvm.ldexp.f32.i32(float [[X]], i32 [[Y]])
+; CHECK-NEXT:    [[LDEXP:%.*]] = select i1 [[COND]], float [[TMP1]], float [[X]]
+; CHECK-NEXT:    ret float [[LDEXP]]
+;
+  %select = select i1 %cond, i32 %y, i32 0
+  %ldexp = call nsz ninf float @llvm.ldexp.f32.i32(float %x, i32 %select)
+  ret float %ldexp
+}
+
+define float @ldexp_f32_mask_select_0_swap(i1 %cond, float %x, i32 %y) {
+; CHECK-LABEL: define float @ldexp_f32_mask_select_0_swap
+; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call float @llvm.ldexp.f32.i32(float [[X]], i32 [[Y]])
+; CHECK-NEXT:    [[LDEXP:%.*]] = select i1 [[COND]], float [[X]], float [[TMP1]]
+; CHECK-NEXT:    ret float [[LDEXP]]
+;
+  %select = select i1 %cond, i32 0, i32 %y
+  %ldexp = call float @llvm.ldexp.f32.i32(float %x, i32 %select)
+  ret float %ldexp
+}
+
+define float @ldexp_f32_mask_select_1(i1 %cond, float %x, i32 %y) {
+; CHECK-LABEL: define float @ldexp_f32_mask_select_1
+; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[COND]], i32 [[Y]], i32 1
+; CHECK-NEXT:    [[LDEXP:%.*]] = call float @llvm.ldexp.f32.i32(float [[X]], i32 [[SELECT]])
+; CHECK-NEXT:    ret float [[LDEXP]]
+;
+  %select = select i1 %cond, i32 %y, i32 1
+  %ldexp = call float @llvm.ldexp.f32.i32(float %x, i32 %select)
+  ret float %ldexp
+}
+
+define float @ldexp_f32_mask_select_0_multi_use(i1 %cond, float %x, i32 %y, ptr addrspace(1) %ptr) {
----------------
dtcxzyw wrote:

```suggestion
define float @ldexp_f32_mask_select_0_multi_use(i1 %cond, float %x, i32 %y, ptr %ptr) {
```

https://github.com/llvm/llvm-project/pull/97354