[llvm] [InstCombine] Preserve the flag from RHS only if the `and` is bitwise (PR #113164)

[via llvm-commits]

https://github.com/XChy created https://github.com/llvm/llvm-project/pull/113164

Fixes #113123
Alive proof: https://alive2.llvm.org/ce/z/hnqeLC

>From f3b8f0d40f4ed698185328860c91d01f22493f97 Mon Sep 17 00:00:00 2001
From: XChy <xxs_chy at outlook.com>
Date: Mon, 21 Oct 2024 21:32:42 +0800
Subject: [PATCH 1/2] [InstCombine] Precommit tests for issue #113123

---
 .../InstCombine/fcmp-range-check-idiom.ll     | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll b/llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll
index 10a3ccf3cdb48a..b7b993764b841b 100644
--- a/llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll
+++ b/llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll
@@ -359,3 +359,42 @@ define i1 @test_and_olt_fmf_propagation_union(float %x) {
   %cond = and i1 %cmp1, %cmp2
   ret i1 %cond
 }
+
+define i1 @test_and_olt_fmf_propagation_union_logical_rhs_poison(float %x) {
+; CHECK-LABEL: define i1 @test_and_olt_fmf_propagation_union_logical_rhs_poison(
+; CHECK-SAME: float [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call ninf float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT:    [[COND:%.*]] = fcmp ninf olt float [[TMP1]], 0x3C00000000000000
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+  %cmp1 = fcmp ninf olt float %x, 0x3C00000000000000
+  %cmp2 = fcmp ogt float %x, 0xBC00000000000000
+  %cond = select i1 %cmp2, i1 %cmp1, i1 false
+  ret i1 %cond
+}
+
+define i1 @test_and_olt_fmf_propagation_union_logical_lhs_poison(float %x) {
+; CHECK-LABEL: define i1 @test_and_olt_fmf_propagation_union_logical_lhs_poison(
+; CHECK-SAME: float [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call ninf float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT:    [[COND:%.*]] = fcmp ninf olt float [[TMP1]], 0x3C00000000000000
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+  %cmp1 = fcmp olt float %x, 0x3C00000000000000
+  %cmp2 = fcmp ninf ogt float %x, 0xBC00000000000000
+  %cond = select i1 %cmp2, i1 %cmp1, i1 false
+  ret i1 %cond
+}
+
+define i1 @test_and_olt_fmf_propagation_union_logical_both_poison(float %x) {
+; CHECK-LABEL: define i1 @test_and_olt_fmf_propagation_union_logical_both_poison(
+; CHECK-SAME: float [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call ninf float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT:    [[COND:%.*]] = fcmp ninf olt float [[TMP1]], 0x3C00000000000000
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+  %cmp1 = fcmp ninf olt float %x, 0x3C00000000000000
+  %cmp2 = fcmp ninf ogt float %x, 0xBC00000000000000
+  %cond = select i1 %cmp2, i1 %cmp1, i1 false
+  ret i1 %cond
+}

>From 44f109f0718f11f55e26538c2658dc1f1f29ab44 Mon Sep 17 00:00:00 2001
From: XChy <xxs_chy at outlook.com>
Date: Mon, 21 Oct 2024 21:35:01 +0800
Subject: [PATCH 2/2] [InstCombine] Only preserve the flags from rhs when the
 and is not logical

---
 llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp    | 6 ++++--
 llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll | 4 ++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index ed9a89b14efcca..678149f56eb901 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1444,8 +1444,10 @@ Value *InstCombinerImpl::foldLogicOfFCmps(FCmpInst *LHS, FCmpInst *RHS,
     }
     if (IsLessThanOrLessEqual(IsAnd ? PredL : PredR)) {
       BuilderTy::FastMathFlagGuard Guard(Builder);
-      Builder.setFastMathFlags(LHS->getFastMathFlags() |
-                               RHS->getFastMathFlags());
+      FastMathFlags NewFlag = LHS->getFastMathFlags();
+      if (!IsLogicalSelect)
+        NewFlag |= RHS->getFastMathFlags();
+      Builder.setFastMathFlags(NewFlag);
 
       Value *FAbs = Builder.CreateUnaryIntrinsic(Intrinsic::fabs, LHS0);
       return Builder.CreateFCmp(PredL, FAbs,
diff --git a/llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll b/llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll
index b7b993764b841b..54dbb09cb8fd31 100644
--- a/llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll
+++ b/llvm/test/Transforms/InstCombine/fcmp-range-check-idiom.ll
@@ -363,8 +363,8 @@ define i1 @test_and_olt_fmf_propagation_union(float %x) {
 define i1 @test_and_olt_fmf_propagation_union_logical_rhs_poison(float %x) {
 ; CHECK-LABEL: define i1 @test_and_olt_fmf_propagation_union_logical_rhs_poison(
 ; CHECK-SAME: float [[X:%.*]]) {
-; CHECK-NEXT:    [[TMP1:%.*]] = call ninf float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT:    [[COND:%.*]] = fcmp ninf olt float [[TMP1]], 0x3C00000000000000
+; CHECK-NEXT:    [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT:    [[COND:%.*]] = fcmp olt float [[TMP1]], 0x3C00000000000000
 ; CHECK-NEXT:    ret i1 [[COND]]
 ;
   %cmp1 = fcmp ninf olt float %x, 0x3C00000000000000