[llvm] [InstCombine] Fix fail to fold (A >> C1) Pred C2 if shr is used multple times #83430 (PR #83563)

[via llvm-commits]

https://github.com/SahilPatidar updated https://github.com/llvm/llvm-project/pull/83563

>From 28dba0b26cd7efd87085657efbfa25c2ad10e3cf Mon Sep 17 00:00:00 2001
From: SahilPatidar <sahilpatidar60 at gmail.com>
Date: Fri, 1 Mar 2024 17:53:01 +0530
Subject: [PATCH 1/2] [InstCombine] Fix fail to fold (A >> C1) Pred C2 if shr
 is used multiple times #83430

---
 llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp       | 2 +-
 .../Transforms/InstCombine/ashr-icmp-minmax-idiom-break.ll    | 3 ++-
 llvm/test/Transforms/InstCombine/icmp-shr-lt-gt.ll            | 4 ++--
 llvm/test/Transforms/InstCombine/icmp-shr.ll                  | 2 +-
 4 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 49e597171b1c6f..0eae03db37f391 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2469,7 +2469,7 @@ Instruction *InstCombinerImpl::foldICmpShrConstant(ICmpInst &Cmp,
   // constant-value-based preconditions in the folds below, then we could assert
   // those conditions rather than checking them. This is difficult because of
   // undef/poison (PR34838).
-  if (IsAShr && Shr->hasOneUse()) {
+  if (IsAShr) {
     if (IsExact || Pred == CmpInst::ICMP_SLT || Pred == CmpInst::ICMP_ULT) {
       // When ShAmtC can be shifted losslessly:
       // icmp PRED (ashr exact X, ShAmtC), C --> icmp PRED X, (C << ShAmtC)
diff --git a/llvm/test/Transforms/InstCombine/ashr-icmp-minmax-idiom-break.ll b/llvm/test/Transforms/InstCombine/ashr-icmp-minmax-idiom-break.ll
index c6d6e916b2c786..0c445b3be3740b 100644
--- a/llvm/test/Transforms/InstCombine/ashr-icmp-minmax-idiom-break.ll
+++ b/llvm/test/Transforms/InstCombine/ashr-icmp-minmax-idiom-break.ll
@@ -10,7 +10,8 @@ define i64 @dont_break_minmax_i64(i64 %conv, i64 %conv2) {
 ; CHECK-SAME: (i64 [[CONV:%.*]], i64 [[CONV2:%.*]]) {
 ; CHECK-NEXT:    [[MUL:%.*]] = mul nsw i64 [[CONV]], [[CONV2]]
 ; CHECK-NEXT:    [[SHR:%.*]] = ashr i64 [[MUL]], 4
-; CHECK-NEXT:    [[SPEC_SELECT_I:%.*]] = call i64 @llvm.smin.i64(i64 [[SHR]], i64 348731)
+; CHECK-NEXT:    [[CMP4_I:%.*]] = icmp slt i64 [[MUL]], 5579712
+; CHECK-NEXT:    [[SPEC_SELECT_I:%.*]] = select i1 [[CMP4_I]], i64 [[SHR]], i64 348731
 ; CHECK-NEXT:    ret i64 [[SPEC_SELECT_I]]
 ;
   %mul = mul nsw i64 %conv, %conv2
diff --git a/llvm/test/Transforms/InstCombine/icmp-shr-lt-gt.ll b/llvm/test/Transforms/InstCombine/icmp-shr-lt-gt.ll
index 1b8efe4351c6dc..08a763a50bf958 100644
--- a/llvm/test/Transforms/InstCombine/icmp-shr-lt-gt.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-shr-lt-gt.ll
@@ -900,7 +900,7 @@ define i1 @ashrsgt_01_00(i4 %x) {
 define i1 @ashrsgt_01_00_multiuse(i4 %x, ptr %p) {
 ; CHECK-LABEL: @ashrsgt_01_00_multiuse(
 ; CHECK-NEXT:    [[S:%.*]] = ashr i4 [[X:%.*]], 1
-; CHECK-NEXT:    [[C:%.*]] = icmp sgt i4 [[S]], 0
+; CHECK-NEXT:    [[C:%.*]] = icmp sgt i4 [[X]], 1
 ; CHECK-NEXT:    store i4 [[S]], ptr [[P:%.*]], align 1
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
@@ -2442,7 +2442,7 @@ define i1 @ashr_sle_noexact(i8 %x) {
 define i1 @ashr_00_00_ashr_extra_use(i8 %x, ptr %ptr) {
 ; CHECK-LABEL: @ashr_00_00_ashr_extra_use(
 ; CHECK-NEXT:    [[S:%.*]] = ashr exact i8 [[X:%.*]], 3
-; CHECK-NEXT:    [[C:%.*]] = icmp ult i8 [[S]], 11
+; CHECK-NEXT:    [[C:%.*]] = icmp ult i8 [[X]], 88
 ; CHECK-NEXT:    store i8 [[S]], ptr [[PTR:%.*]], align 1
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
diff --git a/llvm/test/Transforms/InstCombine/icmp-shr.ll b/llvm/test/Transforms/InstCombine/icmp-shr.ll
index 71b4f5a970c2f6..cdbe9c9e4986fd 100644
--- a/llvm/test/Transforms/InstCombine/icmp-shr.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-shr.ll
@@ -780,7 +780,7 @@ define i1 @ashr_ult_2(i4 %x) {
 define i1 @ashr_ult_2_multiuse(i4 %x, ptr %p) {
 ; CHECK-LABEL: @ashr_ult_2_multiuse(
 ; CHECK-NEXT:    [[S:%.*]] = ashr i4 [[X:%.*]], 1
-; CHECK-NEXT:    [[R:%.*]] = icmp ult i4 [[S]], 2
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i4 [[X]], 4
 ; CHECK-NEXT:    store i4 [[S]], ptr [[P:%.*]], align 1
 ; CHECK-NEXT:    ret i1 [[R]]
 ;

>From da1af627d8b1227e1fe621afc677f68da6de324f Mon Sep 17 00:00:00 2001
From: SahilPatidar <sahilpatidar60 at gmail.com>
Date: Mon, 4 Mar 2024 09:55:35 +0530
Subject: [PATCH 2/2] moves foldICmpWithConstant after the SPF check

---
 llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 0eae03db37f391..4eac73e8055589 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -7025,9 +7025,6 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
   if (Instruction *Res = canonicalizeICmpPredicate(I))
     return Res;
 
-  if (Instruction *Res = foldICmpWithConstant(I))
-    return Res;
-
   if (Instruction *Res = foldICmpWithDominatingICmp(I))
     return Res;
 
@@ -7057,6 +7054,9 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
         return nullptr;
     }
 
+  if (Instruction *Res = foldICmpWithConstant(I))
+    return Res;
+
   // Do this after checking for min/max to prevent infinite looping.
   if (Instruction *Res = foldICmpWithZero(I))
     return Res;