[llvm] [InstCombine] Relax the one-use constraints for `icmp pred (binop X, Z), (binop Y, Z)` (PR #76384)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw updated https://github.com/llvm/llvm-project/pull/76384

>From 7177f67b84c9d20a9e211aa05c21f8cede4206be Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Tue, 26 Dec 2023 19:57:32 +0800
Subject: [PATCH 1/2] [InstCombine] Add pre-commit tests. NFC.

---
 llvm/test/Transforms/InstCombine/icmp.ll | 47 ++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index 1c7bb36f0d34c0..dd5eb3a628323c 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -815,6 +815,53 @@ define i1 @test46(i32 %X, i32 %Y, i32 %Z) {
   ret i1 %C
 }
 
+define i1 @test46_multiuse1(i32 %X, i32 %Y, i32 %Z) {
+; CHECK-LABEL: @test46_multiuse1(
+; CHECK-NEXT:    [[A:%.*]] = ashr exact i32 [[X:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    call void @use_i32(i32 [[A]])
+; CHECK-NEXT:    [[B:%.*]] = ashr exact i32 [[Y:%.*]], [[Z]]
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[A]], [[B]]
+; CHECK-NEXT:    ret i1 [[C]]
+;
+  %A = ashr exact i32 %X, %Z
+  call void @use_i32(i32 %A)
+  %B = ashr exact i32 %Y, %Z
+  %C = icmp ult i32 %A, %B
+  ret i1 %C
+}
+
+define i1 @test46_multiuse2(i32 %X, i32 %Y, i32 %Z) {
+; CHECK-LABEL: @test46_multiuse2(
+; CHECK-NEXT:    [[A:%.*]] = ashr exact i32 [[X:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    [[B:%.*]] = ashr exact i32 [[Y:%.*]], [[Z]]
+; CHECK-NEXT:    call void @use_i32(i32 [[B]])
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[A]], [[B]]
+; CHECK-NEXT:    ret i1 [[C]]
+;
+  %A = ashr exact i32 %X, %Z
+  %B = ashr exact i32 %Y, %Z
+  call void @use_i32(i32 %B)
+  %C = icmp ult i32 %A, %B
+  ret i1 %C
+}
+
+define i1 @test46_multiuse3(i32 %X, i32 %Y, i32 %Z) {
+; CHECK-LABEL: @test46_multiuse3(
+; CHECK-NEXT:    [[A:%.*]] = ashr exact i32 [[X:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    call void @use_i32(i32 [[A]])
+; CHECK-NEXT:    [[B:%.*]] = ashr exact i32 [[Y:%.*]], [[Z]]
+; CHECK-NEXT:    call void @use_i32(i32 [[B]])
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[A]], [[B]]
+; CHECK-NEXT:    ret i1 [[C]]
+;
+  %A = ashr exact i32 %X, %Z
+  call void @use_i32(i32 %A)
+  %B = ashr exact i32 %Y, %Z
+  call void @use_i32(i32 %B)
+  %C = icmp ult i32 %A, %B
+  ret i1 %C
+}
+
 ; PR9343 #5
 define i1 @test47(i32 %X, i32 %Y, i32 %Z) {
 ; CHECK-LABEL: @test47(

>From aa888125d682f68804d31c1449cf3b188c1af6e2 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2333 at gmail.com>
Date: Tue, 26 Dec 2023 21:26:38 +0800
Subject: [PATCH 2/2] [InstCombine] Relax the one-use constraints for `icmp
 pred (binop X, Z), (binop Y, Z)`

---
 llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 5 +++--
 llvm/test/Transforms/InstCombine/icmp.ll                | 8 +++-----
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 289976718e52f3..1e1d09843b13ec 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4911,8 +4911,9 @@ Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,
     }
   }
 
-  if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
-      BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
+  if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() &&
+      (BO0->hasOneUse() || BO1->hasOneUse()) &&
+      BO0->getOperand(1) == BO1->getOperand(1)) {
     switch (BO0->getOpcode()) {
     default:
       break;
diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index dd5eb3a628323c..5b0c1f58bd8820 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -819,8 +819,7 @@ define i1 @test46_multiuse1(i32 %X, i32 %Y, i32 %Z) {
 ; CHECK-LABEL: @test46_multiuse1(
 ; CHECK-NEXT:    [[A:%.*]] = ashr exact i32 [[X:%.*]], [[Z:%.*]]
 ; CHECK-NEXT:    call void @use_i32(i32 [[A]])
-; CHECK-NEXT:    [[B:%.*]] = ashr exact i32 [[Y:%.*]], [[Z]]
-; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[A]], [[B]]
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[X]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
   %A = ashr exact i32 %X, %Z
@@ -832,10 +831,9 @@ define i1 @test46_multiuse1(i32 %X, i32 %Y, i32 %Z) {
 
 define i1 @test46_multiuse2(i32 %X, i32 %Y, i32 %Z) {
 ; CHECK-LABEL: @test46_multiuse2(
-; CHECK-NEXT:    [[A:%.*]] = ashr exact i32 [[X:%.*]], [[Z:%.*]]
-; CHECK-NEXT:    [[B:%.*]] = ashr exact i32 [[Y:%.*]], [[Z]]
+; CHECK-NEXT:    [[B:%.*]] = ashr exact i32 [[Y:%.*]], [[Z:%.*]]
 ; CHECK-NEXT:    call void @use_i32(i32 [[B]])
-; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[A]], [[B]]
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i32 [[X:%.*]], [[Y]]
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
   %A = ashr exact i32 %X, %Z