[llvm] f48f178 - [InstCombine] canonicalize cmp+select as smin/smax

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2023-02-12T07:54:43-05:00
New Revision: f48f178717927e77c42ef17de42688b8a60733e3

URL: https://github.com/llvm/llvm-project/commit/f48f178717927e77c42ef17de42688b8a60733e3
DIFF: https://github.com/llvm/llvm-project/commit/f48f178717927e77c42ef17de42688b8a60733e3.diff

LOG: [InstCombine] canonicalize cmp+select as smin/smax

(V == SMIN) ? SMIN+1 : V --> smax(V, SMIN+1)
(V == SMAX) ? SMAX-1 : V --> smin(V, SMAX-1)

https://alive2.llvm.org/ce/z/d5bqjy

Follow-up for the unsigned variants added with:
86b4d8645fc1b866

issue #60374

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
    llvm/test/Transforms/InstCombine/select.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 894b11c9d918c..cefd0acbc9bf9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1605,12 +1605,18 @@ static Value *foldSelectInstWithICmpConst(SelectInst &SI, ICmpInst *ICI,
   Value *TVal = SI.getTrueValue();
   Value *FVal = SI.getFalseValue();
   if (Pred == ICmpInst::ICMP_EQ && V == FVal) {
-    // (V == 0) ? 1 : V --> umax(V, 1)
+    // (V == UMIN) ? UMIN+1 : V --> umax(V, UMIN+1)
     if (CmpC->isMinValue() && match(TVal, m_SpecificInt(*CmpC + 1)))
       return Builder.CreateBinaryIntrinsic(Intrinsic::umax, V, TVal);
     // (V == UMAX) ? UMAX-1 : V --> umin(V, UMAX-1)
     if (CmpC->isMaxValue() && match(TVal, m_SpecificInt(*CmpC - 1)))
       return Builder.CreateBinaryIntrinsic(Intrinsic::umin, V, TVal);
+    // (V == SMIN) ? SMIN+1 : V --> smax(V, SMIN+1)
+    if (CmpC->isMinSignedValue() && match(TVal, m_SpecificInt(*CmpC + 1)))
+      return Builder.CreateBinaryIntrinsic(Intrinsic::smax, V, TVal);
+    // (V == SMAX) ? SMAX-1 : V --> smin(V, SMAX-1)
+    if (CmpC->isMaxSignedValue() && match(TVal, m_SpecificInt(*CmpC - 1)))
+      return Builder.CreateBinaryIntrinsic(Intrinsic::smin, V, TVal);
   }
 
   BinaryOperator *BO;

diff  --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index ab38bd1787311..20e9a3aa0312a 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -3484,8 +3484,7 @@ define i8 @not_clamp_umax2(i8 %x) {
 
 define i8 @clamp_smin(i8 %x) {
 ; CHECK-LABEL: @clamp_smin(
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[X:%.*]], -128
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i8 -127, i8 [[X]]
+; CHECK-NEXT:    [[SEL:%.*]] = call i8 @llvm.smax.i8(i8 [[X:%.*]], i8 -127)
 ; CHECK-NEXT:    ret i8 [[SEL]]
 ;
   %cmp = icmp eq i8 %x, -128
@@ -3497,7 +3496,7 @@ define i8 @clamp_smin_use(i8 %x) {
 ; CHECK-LABEL: @clamp_smin_use(
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[X:%.*]], -128
 ; CHECK-NEXT:    call void @use1(i1 [[CMP]])
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i8 -127, i8 [[X]]
+; CHECK-NEXT:    [[SEL:%.*]] = call i8 @llvm.smax.i8(i8 [[X]], i8 -127)
 ; CHECK-NEXT:    ret i8 [[SEL]]
 ;
   %cmp = icmp eq i8 %x, -128
@@ -3534,8 +3533,7 @@ define i8 @not_clamp_smin2(i8 %x) {
 
 define <2 x i8> @clamp_smaxval(<2 x i8> %x) {
 ; CHECK-LABEL: @clamp_smaxval(
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i8> [[X:%.*]], <i8 127, i8 127>
-; CHECK-NEXT:    [[SEL:%.*]] = select <2 x i1> [[CMP]], <2 x i8> <i8 126, i8 126>, <2 x i8> [[X]]
+; CHECK-NEXT:    [[SEL:%.*]] = call <2 x i8> @llvm.smin.v2i8(<2 x i8> [[X:%.*]], <2 x i8> <i8 126, i8 126>)
 ; CHECK-NEXT:    ret <2 x i8> [[SEL]]
 ;
   %cmp = icmp eq <2 x i8> %x, <i8 127, i8 127>