[llvm] [InstCombine] Enable select freeze poison folding when storing value (PR #129776)

[Nikita Popov via llvm-commits]

================
@@ -4930,12 +4963,88 @@ define void @select_freeze_poison_global(ptr %addr.tgt, i1 %cond) {
 
 define void @select_freeze_poison_constant(ptr %addr.tgt, i1 %cond) {
 ; CHECK-LABEL: @select_freeze_poison_constant(
-; CHECK-NEXT:    [[SELECT_ADDR:%.*]] = select i1 [[COND:%.*]], i32 72, i32 0
-; CHECK-NEXT:    store i32 [[SELECT_ADDR]], ptr [[ADDR_TGT:%.*]], align 4
+; CHECK-NEXT:    store i32 72, ptr [[ADDR_TGT:%.*]], align 4
 ; CHECK-NEXT:    ret void
 ;
   %freeze = freeze i32 poison
   %select.addr = select i1 %cond, i32 72, i32 %freeze
   store i32 %select.addr, ptr %addr.tgt
   ret void
 }
+
+define <2 x i8> @select_freeze_poison_mask_vector(i1 %cond, <2 x i8> noundef %y) {
+; CHECK-LABEL: @select_freeze_poison_mask_vector(
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x i8> [[Y:%.*]], <2 x i8> zeroinitializer
+; CHECK-NEXT:    ret <2 x i8> [[SEL]]
+;
+  %freeze = freeze <2 x i8> <i8 0, i8 poison>
+  %sel = select i1 %cond, <2 x i8> %y, <2 x i8> %freeze
+  ret <2 x i8> %sel
+}
+
+define <2 x i8> @selects_freeze_poison_mask_vector(<2 x i8> noundef %x, i1 %cond1, i1 %cond2) {
+; CHECK-LABEL: @selects_freeze_poison_mask_vector(
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[COND1:%.*]], i1 [[COND2:%.*]], i1 false
+; CHECK-NEXT:    [[X:%.*]] = select i1 [[TMP1]], <2 x i8> [[X1:%.*]], <2 x i8> zeroinitializer
+; CHECK-NEXT:    ret <2 x i8> [[X]]
+;
+  %freeze = freeze <2 x i8> <i8 0, i8 poison>
+  %sel1 = select i1 %cond1, <2 x i8> %x, <2 x i8> %freeze
+  %sel2 = select i1 %cond2, <2 x i8> %x, <2 x i8> %freeze
+  %conj = and <2 x i8> %sel1, %sel2
+  ret <2 x i8> %conj
+}
+
+define <2 x i8> @select_freeze_poison_splat_vector(i1 %cond, <2 x i8> noundef %y) {
+; CHECK-LABEL: @select_freeze_poison_splat_vector(
+; CHECK-NEXT:    ret <2 x i8> [[Y:%.*]]
+;
+  %freeze = freeze <2 x i8> <i8 poison, i8 poison>
+  %sel = select i1 %cond, <2 x i8> %y, <2 x i8> %freeze
+  ret <2 x i8> %sel
+}
+
+define <2 x i8> @selects_freeze_poison_splat_vector(<2 x i8> noundef %x, i1 %cond1, i1 %cond2) {
+; CHECK-LABEL: @selects_freeze_poison_splat_vector(
+; CHECK-NEXT:    ret <2 x i8> [[X:%.*]]
+;
+  %freeze = freeze <2 x i8> <i8 poison, i8 poison>
+  %sel1 = select i1 %cond1, <2 x i8> %x, <2 x i8> %freeze
+  %sel2 = select i1 %cond2, <2 x i8> %x, <2 x i8> %freeze
+  %conj = and <2 x i8> %sel1, %sel2
+  ret <2 x i8> %conj
+}
+
+define <2 x i8> @select_freeze_constant_vector(i1 %cond, <2 x i8> noundef %y) {
+; CHECK-LABEL: @select_freeze_constant_vector(
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x i8> [[Y:%.*]], <2 x i8> zeroinitializer
+; CHECK-NEXT:    ret <2 x i8> [[SEL]]
+;
+  %freeze = freeze <2 x i8> <i8 0, i8 0>
+  %sel = select i1 %cond, <2 x i8> %y, <2 x i8> %freeze
+  ret <2 x i8> %sel
+}
+
+define <2 x i8> @select_freeze_constant_expression_vector_add(i1 %cond, <2 x i8> noundef %y) {
+; CHECK-LABEL: @select_freeze_constant_expression_vector_add(
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x i8> [[Y:%.*]], <2 x i8> splat (i8 3)
+; CHECK-NEXT:    ret <2 x i8> [[SEL]]
+;
+  %freeze = freeze <2 x i8> <i8 poison, i8 add (i8 1, i8 2)>
+  %sel = select i1 %cond, <2 x i8> %y, <2 x i8> %freeze
+  ret <2 x i8> %sel
+}
+
+%struct.1 = type {i32, i32}
+ at glb.struct.1 = global %struct.1 {i32 1, i32 2}
+
+define <2 x ptr> @select_freeze_constant_expression_vector_gep(i1 %cond, <2 x ptr> noundef %y) {
+; CHECK-LABEL: @select_freeze_constant_expression_vector_gep(
+; CHECK-NEXT:    [[FREEZE:%.*]] = freeze <2 x ptr> <ptr poison, ptr getelementptr inbounds nuw (i8, ptr @glb.struct.1, i64 4)>
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x ptr> [[Y:%.*]], <2 x ptr> [[FREEZE]]
+; CHECK-NEXT:    ret <2 x ptr> [[SEL]]
+;
+  %freeze = freeze <2 x ptr> <ptr poison, ptr getelementptr (%struct.1, ptr @glb.struct.1, i64 0, i32 1)>
----------------
nikic wrote:

```suggestion
  %freeze = freeze <2 x ptr> <ptr poison, ptr getelementptr inbounds (%struct.1, ptr @glb.struct.1, i64 100)>
```
I'd do something like this, to make the constant expression indirectly poison.

https://github.com/llvm/llvm-project/pull/129776