InstCombine: Add test for bugzilla 44242

[arsenm]

LGTM

[cwabbott]

Add a test for multiple phis as suggested by @nikic.

llvm/test/Transforms/InstCombine/pr44242.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+; Check that we don't create two redundant phi nodes when %val is used in a
+; form where we can't rewrite it in terms of the new phi node.
+
+; Use %val in an instruction type not supported by optimizeBitCastFromPhi.
+define float @sitofp(float %x) {
+; CHECK-LABEL: @sitofp(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
+; CHECK:       loop_header:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi float [ 0.000000e+00, [[ENTRY:%.*]] ], [ [[VAL_INCR:%.*]], [[LOOP:%.*]] ]
+; CHECK-NEXT:    [[VAL:%.*]] = phi float [ 0.000000e+00, [[ENTRY]] ], [ [[PHITMP:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = fcmp ogt float [[TMP0]], [[X:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[END:%.*]], label [[LOOP]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[VAL_INCR]] = fadd float [[TMP0]], 1.000000e+00
+; CHECK-NEXT:    [[VAL_INCR_CASTED:%.*]] = bitcast float [[VAL_INCR]] to i32
+; CHECK-NEXT:    [[PHITMP]] = sitofp i32 [[VAL_INCR_CASTED]] to float
+; CHECK-NEXT:    br label [[LOOP_HEADER]]
+; CHECK:       end:
+; CHECK-NEXT:    ret float [[VAL]]
+;
+entry:
+  br label %loop_header
+loop_header:
+  %val = phi i32 [ 0, %entry ], [ %val_incr_casted, %loop ]
+  %val_casted = bitcast i32 %val to float
+  %cmp = fcmp ogt float %val_casted, %x
+  br i1 %cmp, label %end, label %loop
+loop:
+  %val_incr = fadd float %val_casted, 1.0
+  %val_incr_casted = bitcast float %val_incr to i32
+  br label %loop_header
+end:
+  %result = sitofp i32 %val to float
+  ret float %result
+}
+
+; Use %val in an incompatible bitcast.
+define <2 x i16> @bitcast(float %x) {
+; CHECK-LABEL: @bitcast(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
+; CHECK:       loop_header:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi float [ 0.000000e+00, [[ENTRY:%.*]] ], [ [[VAL_INCR:%.*]], [[LOOP:%.*]] ]
+; CHECK-NEXT:    [[VAL:%.*]] = phi <2 x i16> [ zeroinitializer, [[ENTRY]] ], [ [[PHITMP:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = fcmp ogt float [[TMP0]], [[X:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[END:%.*]], label [[LOOP]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[VAL_INCR]] = fadd float [[TMP0]], 1.000000e+00
+; CHECK-NEXT:    [[PHITMP]] = bitcast float [[VAL_INCR]] to <2 x i16>
+; CHECK-NEXT:    br label [[LOOP_HEADER]]
+; CHECK:       end:
+; CHECK-NEXT:    ret <2 x i16> [[VAL]]
+;
+entry:
+  br label %loop_header
+loop_header:
+  %val = phi i32 [ 0, %entry ], [ %val_incr_casted, %loop ]
+  %val_casted = bitcast i32 %val to float
+  %cmp = fcmp ogt float %val_casted, %x
+  br i1 %cmp, label %end, label %loop
+loop:
+  %val_incr = fadd float %val_casted, 1.0
+  %val_incr_casted = bitcast float %val_incr to i32
+  br label %loop_header
+end:
+  %result = bitcast i32 %val to <2 x i16>
+  ret <2 x i16> %result
+}
+
+@global = global i32 0
+
+; Use %val with a volatile store.
+define void @store_volatile(float %x) {
+; CHECK-LABEL: @store_volatile(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
+; CHECK:       loop_header:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi float [ 0.000000e+00, [[ENTRY:%.*]] ], [ [[VAL_INCR:%.*]], [[LOOP:%.*]] ]
+; CHECK-NEXT:    [[VAL:%.*]] = phi i32 [ 0, [[ENTRY]] ], [ [[VAL_INCR_CASTED:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = fcmp ogt float [[TMP0]], [[X:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[END:%.*]], label [[LOOP]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[VAL_INCR]] = fadd float [[TMP0]], 1.000000e+00
+; CHECK-NEXT:    [[VAL_INCR_CASTED]] = bitcast float [[VAL_INCR]] to i32
+; CHECK-NEXT:    br label [[LOOP_HEADER]]
+; CHECK:       end:
+; CHECK-NEXT:    store volatile i32 [[VAL]], i32* @global, align 4
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %loop_header
+loop_header:
+  %val = phi i32 [ 0, %entry ], [ %val_incr_casted, %loop ]
+  %val_casted = bitcast i32 %val to float
+  %cmp = fcmp ogt float %val_casted, %x
+  br i1 %cmp, label %end, label %loop
+loop:
+  %val_incr = fadd float %val_casted, 1.0
+  %val_incr_casted = bitcast float %val_incr to i32
+  br label %loop_header
+end:
+  store volatile i32 %val, i32* @global
+  ret void
+}
+
+; Use %val with a store where it's actually the address.
+define void @store_address(i32 %x) {
+; CHECK-LABEL: @store_address(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
+; CHECK:       loop_header:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi float* [ bitcast (i32* @global to float*), [[ENTRY:%.*]] ], [ [[VAL_INCR:%.*]], [[LOOP:%.*]] ]
+; CHECK-NEXT:    [[VAL:%.*]] = phi i32* [ @global, [[ENTRY]] ], [ [[VAL_INCR_CASTED:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[X:%.*]], 0
+; CHECK-NEXT:    br i1 [[CMP]], label [[END:%.*]], label [[LOOP]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[VAL_INCR]] = getelementptr float, float* [[TMP0]], i64 1
+; CHECK-NEXT:    [[VAL_INCR_CASTED]] = bitcast float* [[VAL_INCR]] to i32*
+; CHECK-NEXT:    br label [[LOOP_HEADER]]
+; CHECK:       end:
+; CHECK-NEXT:    store i32 0, i32* [[VAL]], align 4
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %loop_header
+loop_header:
+  %val = phi i32* [ @global, %entry ], [ %val_incr_casted, %loop ]
+  %i = phi i32 [ 0, %entry ], [ %i_incr, %loop ]
+  %val_casted = bitcast i32* %val to float*
+  %cmp = icmp sgt i32 %i, %x
+  br i1 %cmp, label %end, label %loop
+loop:
+  %i_incr = add i32 %i, 0
+  %val_incr = getelementptr float, float* %val_casted, i32 1
+  %val_incr_casted = bitcast float* %val_incr to i32*
+  br label %loop_header
+end:
+  store i32 0, i32* %val
+  ret void
+}
+
+; Test where a phi (%val2) other than the original one (%val) has an
+; incompatible use.
+define i32 @multiple_phis(float %x) {
+; CHECK-LABEL: @multiple_phis(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
+; CHECK:       loop_header:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi float [ 0.000000e+00, [[ENTRY:%.*]] ], [ [[TMP1:%.*]], [[LOOP_END:%.*]] ]
+; CHECK-NEXT:    [[VAL:%.*]] = phi i32 [ 0, [[ENTRY]] ], [ [[VAL2:%.*]], [[LOOP_END]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = fcmp ogt float [[TMP0]], [[X:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[END:%.*]], label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[CMP2:%.*]] = fcmp ogt float [[TMP0]], 2.000000e+00
+; CHECK-NEXT:    br i1 [[CMP2]], label [[IF:%.*]], label [[LOOP_END]]
+; CHECK:       if:
+; CHECK-NEXT:    [[VAL_INCR:%.*]] = fadd float [[TMP0]], 1.000000e+00
+; CHECK-NEXT:    [[VAL_INCR_CASTED:%.*]] = bitcast float [[VAL_INCR]] to i32
+; CHECK-NEXT:    br label [[LOOP_END]]
+; CHECK:       loop_end:
+; CHECK-NEXT:    [[TMP1]] = phi float [ [[TMP0]], [[LOOP]] ], [ [[VAL_INCR]], [[IF]] ]
+; CHECK-NEXT:    [[VAL2]] = phi i32 [ [[VAL]], [[LOOP]] ], [ [[VAL_INCR_CASTED]], [[IF]] ]
+; CHECK-NEXT:    store volatile i32 [[VAL2]], i32* @global, align 4
+; CHECK-NEXT:    br label [[LOOP_HEADER]]
+; CHECK:       end:
+; CHECK-NEXT:    ret i32 [[VAL]]
+;
+entry:
+  br label %loop_header
+loop_header:
+  %val = phi i32 [ 0, %entry ], [ %val2, %loop_end ]
+  %val_casted = bitcast i32 %val to float
+  %cmp = fcmp ogt float %val_casted, %x
+  br i1 %cmp, label %end, label %loop
+loop:
+  %cmp2 = fcmp ogt float %val_casted, 2.0
+  br i1 %cmp2, label %if, label %loop_end
+if:
+  %val_incr = fadd float %val_casted, 1.0
+  %val_incr_casted = bitcast float %val_incr to i32
+  br label %loop_end
+loop_end:
+  %val2 = phi i32 [ %val, %loop ], [ %val_incr_casted, %if ]
+  store volatile i32 %val2, i32* @global ; the incompatible use
+  br label %loop_header
+end:
+  ret i32 %val
+}