Revert "[InstCombine] Teach foldSelectOpOp about samesign"

[alexfh]

Reverts #122723 due to a miscompilation

See #122723 (comment) for details and the test case.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Alexander Kornienko (alexfh)

Changes

Reverts llvm/llvm-project#122723 due to a miscompilation

See #122723 (comment) for details and the test case.

---

Full diff: https://github.com/llvm/llvm-project/pull/124123.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp (+4-4)
• (modified) llvm/test/Transforms/InstCombine/select-cmp.ll (-96)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index d5d9a829c3068a..f66a976ccb47fe 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -428,10 +428,10 @@ Instruction *InstCombinerImpl::foldSelectOpOp(SelectInst &SI, Instruction *TI,
     CmpPredicate TPred, FPred;
     if (match(TI, m_ICmp(TPred, m_Value(), m_Value())) &&
         match(FI, m_ICmp(FPred, m_Value(), m_Value()))) {
-      bool Swapped = ICmpInst::isRelational(FPred) &&
-                     CmpPredicate::getMatching(
-                         TPred, ICmpInst::getSwappedCmpPredicate(FPred));
-      if (CmpPredicate::getMatching(TPred, FPred) || Swapped) {
+      // FIXME: Use CmpPredicate::getMatching here.
+      CmpInst::Predicate T = TPred, F = FPred;
+      if (T == F || T == ICmpInst::getSwappedCmpPredicate(F)) {
+        bool Swapped = T != F;
         if (Value *MatchOp =
                 getCommonOp(TI, FI, ICmpInst::isEquality(TPred), Swapped)) {
           Value *NewSel = Builder.CreateSelect(Cond, OtherOpT, OtherOpF,
diff --git a/llvm/test/Transforms/InstCombine/select-cmp.ll b/llvm/test/Transforms/InstCombine/select-cmp.ll
index 7e5d5821d9f6a7..f7505bd85f89eb 100644
--- a/llvm/test/Transforms/InstCombine/select-cmp.ll
+++ b/llvm/test/Transforms/InstCombine/select-cmp.ll
@@ -23,18 +23,6 @@ define i1 @icmp_ne_common_op00(i1 %c, i6 %x, i6 %y, i6 %z) {
   ret i1 %r
 }
 
-define i1 @icmp_ne_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
-; CHECK-LABEL: @icmp_ne_samesign_common(
-; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i6 [[X:%.*]], [[R_V]]
-; CHECK-NEXT:    ret i1 [[R]]
-;
-  %cmp1 = icmp samesign ne i6 %x, %y
-  %cmp2 = icmp ne i6 %x, %z
-  %r = select i1 %c, i1 %cmp1, i1 %cmp2
-  ret i1 %r
-}
-
 define i1 @icmp_ne_common_op01(i1 %c, i3 %x, i3 %y, i3 %z) {
 ; CHECK-LABEL: @icmp_ne_common_op01(
 ; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i3 [[Y:%.*]], i3 [[Z:%.*]]
@@ -83,18 +71,6 @@ define i1 @icmp_eq_common_op00(i1 %c, i5 %x, i5 %y, i5 %z) {
   ret i1 %r
 }
 
-define i1 @icmp_eq_samesign_common(i1 %c, i5 %x, i5 %y, i5 %z) {
-; CHECK-LABEL: @icmp_eq_samesign_common(
-; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i5 [[Y:%.*]], i5 [[Z:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i5 [[X:%.*]], [[R_V]]
-; CHECK-NEXT:    ret i1 [[R]]
-;
-  %cmp1 = icmp eq i5 %x, %y
-  %cmp2 = icmp samesign eq i5 %x, %z
-  %r = select i1 %c, i1 %cmp1, i1 %cmp2
-  ret i1 %r
-}
-
 define <5 x i1> @icmp_eq_common_op01(<5 x i1> %c, <5 x i7> %x, <5 x i7> %y, <5 x i7> %z) {
 ; CHECK-LABEL: @icmp_eq_common_op01(
 ; CHECK-NEXT:    [[R_V:%.*]] = select <5 x i1> [[C:%.*]], <5 x i7> [[Y:%.*]], <5 x i7> [[Z:%.*]]
@@ -158,18 +134,6 @@ define i1 @icmp_slt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
   ret i1 %r
 }
 
-define i1 @icmp_slt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
-; CHECK-LABEL: @icmp_slt_samesign_common(
-; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ult i6 [[X:%.*]], [[R_V]]
-; CHECK-NEXT:    ret i1 [[R]]
-;
-  %cmp1 = icmp samesign ult i6 %x, %y
-  %cmp2 = icmp slt i6 %x, %z
-  %r = select i1 %c, i1 %cmp1, i1 %cmp2
-  ret i1 %r
-}
-
 define i1 @icmp_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
 ; CHECK-LABEL: @icmp_sgt_common(
 ; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -182,18 +146,6 @@ define i1 @icmp_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
   ret i1 %r
 }
 
-define i1 @icmp_sgt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
-; CHECK-LABEL: @icmp_sgt_samesign_common(
-; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ugt i6 [[X:%.*]], [[R_V]]
-; CHECK-NEXT:    ret i1 [[R]]
-;
-  %cmp1 = icmp samesign ugt i6 %x, %y
-  %cmp2 = icmp sgt i6 %x, %z
-  %r = select i1 %c, i1 %cmp1, i1 %cmp2
-  ret i1 %r
-}
-
 define i1 @icmp_sle_common(i1 %c, i6 %x, i6 %y, i6 %z) {
 ; CHECK-LABEL: @icmp_sle_common(
 ; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -206,18 +158,6 @@ define i1 @icmp_sle_common(i1 %c, i6 %x, i6 %y, i6 %z) {
   ret i1 %r
 }
 
-define i1 @icmp_sle_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
-; CHECK-LABEL: @icmp_sle_samesign_common(
-; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sge i6 [[X:%.*]], [[R_V]]
-; CHECK-NEXT:    ret i1 [[R]]
-;
-  %cmp1 = icmp sle i6 %y, %x
-  %cmp2 = icmp samesign ule i6 %z, %x
-  %r = select i1 %c, i1 %cmp1, i1 %cmp2
-  ret i1 %r
-}
-
 define i1 @icmp_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
 ; CHECK-LABEL: @icmp_sge_common(
 ; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -230,18 +170,6 @@ define i1 @icmp_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
   ret i1 %r
 }
 
-define i1 @icmp_sge_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
-; CHECK-LABEL: @icmp_sge_samesign_common(
-; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sle i6 [[X:%.*]], [[R_V]]
-; CHECK-NEXT:    ret i1 [[R]]
-;
-  %cmp1 = icmp sge i6 %y, %x
-  %cmp2 = icmp samesign uge i6 %z, %x
-  %r = select i1 %c, i1 %cmp1, i1 %cmp2
-  ret i1 %r
-}
-
 define i1 @icmp_slt_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
 ; CHECK-LABEL: @icmp_slt_sgt_common(
 ; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -254,18 +182,6 @@ define i1 @icmp_slt_sgt_common(i1 %c, i6 %x, i6 %y, i6 %z) {
   ret i1 %r
 }
 
-define i1 @icmp_slt_sgt_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
-; CHECK-LABEL: @icmp_slt_sgt_samesign_common(
-; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ult i6 [[X:%.*]], [[R_V]]
-; CHECK-NEXT:    ret i1 [[R]]
-;
-  %cmp1 = icmp samesign ult i6 %x, %y
-  %cmp2 = icmp sgt i6 %z, %x
-  %r = select i1 %c, i1 %cmp1, i1 %cmp2
-  ret i1 %r
-}
-
 define i1 @icmp_sle_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
 ; CHECK-LABEL: @icmp_sle_sge_common(
 ; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
@@ -278,18 +194,6 @@ define i1 @icmp_sle_sge_common(i1 %c, i6 %x, i6 %y, i6 %z) {
   ret i1 %r
 }
 
-define i1 @icmp_sle_sge_samesign_common(i1 %c, i6 %x, i6 %y, i6 %z) {
-; CHECK-LABEL: @icmp_sle_sge_samesign_common(
-; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sge i6 [[X:%.*]], [[R_V]]
-; CHECK-NEXT:    ret i1 [[R]]
-;
-  %cmp1 = icmp sle i6 %y, %x
-  %cmp2 = icmp samesign uge i6 %x, %z
-  %r = select i1 %c, i1 %cmp1, i1 %cmp2
-  ret i1 %r
-}
-
 define i1 @icmp_ult_common(i1 %c, i6 %x, i6 %y, i6 %z) {
 ; CHECK-LABEL: @icmp_ult_common(
 ; CHECK-NEXT:    [[R_V:%.*]] = select i1 [[C:%.*]], i6 [[Y:%.*]], i6 [[Z:%.*]]

[artagnon]

I don't think #122723 is problematic per-se, but I think it exposed an underlying problem: I need more time to investigate. However, I think the revert is okay while we investigate the problem, but would defer to @nikic on the final approval.

[goldsteinn]

Unless the fix is obvious / immediate, should revert.

[artagnon]

Since one other person (@goldsteinn) has verified, this should land without delay.

[nikic]

LGTM