[llvm-branch-commits] [llvm] f4006c5 - [InstSimplify] fold min/max with limit constant
Tom Stellard via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Mon Aug 16 11:35:58 PDT 2021
Author: Sanjay Patel
Date: 2021-08-16T11:35:29-07:00
New Revision: f4006c59497d425f5a3df5e68da5add21f8e467d
URL: https://github.com/llvm/llvm-project/commit/f4006c59497d425f5a3df5e68da5add21f8e467d
DIFF: https://github.com/llvm/llvm-project/commit/f4006c59497d425f5a3df5e68da5add21f8e467d.diff
LOG: [InstSimplify] fold min/max with limit constant
This is already done within InstCombine:
https://alive2.llvm.org/ce/z/MiGE22
...but leaving it out of analysis makes it
harder to avoid infinite loops there.
(cherry picked from commit e260e10c4a21784c146c94a2a14b7e78b09a9cf7)
Added:
Modified:
llvm/include/llvm/Analysis/ValueTracking.h
llvm/lib/Analysis/InstructionSimplify.cpp
llvm/lib/Analysis/ValueTracking.cpp
llvm/test/Transforms/InstSimplify/maxmin.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/ValueTracking.h b/llvm/include/llvm/Analysis/ValueTracking.h
index 90ec742f18e67..f46e66641c082 100644
--- a/llvm/include/llvm/Analysis/ValueTracking.h
+++ b/llvm/include/llvm/Analysis/ValueTracking.h
@@ -744,6 +744,10 @@ constexpr unsigned MaxAnalysisRecursionDepth = 6;
/// minimum/maximum flavor.
CmpInst::Predicate getInverseMinMaxPred(SelectPatternFlavor SPF);
+ /// Return the minimum or maximum constant value for the specified integer
+ /// min/max flavor and type.
+ APInt getMinMaxLimit(SelectPatternFlavor SPF, unsigned BitWidth);
+
/// Check if the values in \p VL are select instructions that can be converted
/// to a min or max (vector) intrinsic. Returns the intrinsic ID, if such a
/// conversion is possible, together with a bool indicating whether all select
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 23083bc8178e7..69ab0052b0a74 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4080,6 +4080,22 @@ static Value *simplifySelectWithICmpCond(Value *CondVal, Value *TrueVal,
std::swap(TrueVal, FalseVal);
}
+ // Check for integer min/max with a limit constant:
+ // X > MIN_INT ? X : MIN_INT --> X
+ // X < MAX_INT ? X : MAX_INT --> X
+ if (TrueVal->getType()->isIntOrIntVectorTy()) {
+ Value *X, *Y;
+ SelectPatternFlavor SPF =
+ matchDecomposedSelectPattern(cast<ICmpInst>(CondVal), TrueVal, FalseVal,
+ X, Y).Flavor;
+ if (SelectPatternResult::isMinOrMax(SPF) && Pred == getMinMaxPred(SPF)) {
+ APInt LimitC = getMinMaxLimit(getInverseMinMaxFlavor(SPF),
+ X->getType()->getScalarSizeInBits());
+ if (match(Y, m_SpecificInt(LimitC)))
+ return X;
+ }
+ }
+
if (Pred == ICmpInst::ICMP_EQ && match(CmpRHS, m_Zero())) {
Value *X;
const APInt *Y;
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 522d21812c6a5..6e3ca5c4e08ae 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -6253,6 +6253,16 @@ CmpInst::Predicate llvm::getInverseMinMaxPred(SelectPatternFlavor SPF) {
return getMinMaxPred(getInverseMinMaxFlavor(SPF));
}
+APInt llvm::getMinMaxLimit(SelectPatternFlavor SPF, unsigned BitWidth) {
+ switch (SPF) {
+ case SPF_SMAX: return APInt::getSignedMaxValue(BitWidth);
+ case SPF_SMIN: return APInt::getSignedMinValue(BitWidth);
+ case SPF_UMAX: return APInt::getMaxValue(BitWidth);
+ case SPF_UMIN: return APInt::getMinValue(BitWidth);
+ default: llvm_unreachable("Unexpected flavor");
+ }
+}
+
std::pair<Intrinsic::ID, bool>
llvm::canConvertToMinOrMaxIntrinsic(ArrayRef<Value *> VL) {
// Check if VL contains select instructions that can be folded into a min/max
diff --git a/llvm/test/Transforms/InstSimplify/maxmin.ll b/llvm/test/Transforms/InstSimplify/maxmin.ll
index e9fff33f63114..1dea800e6ecd0 100644
--- a/llvm/test/Transforms/InstSimplify/maxmin.ll
+++ b/llvm/test/Transforms/InstSimplify/maxmin.ll
@@ -3,9 +3,7 @@
define i8 @smax_min_limit(i8 %x) {
; CHECK-LABEL: @smax_min_limit(
-; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -128
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[X]], i8 -128
-; CHECK-NEXT: ret i8 [[SEL]]
+; CHECK-NEXT: ret i8 [[X:%.*]]
;
%cmp = icmp sgt i8 %x, -128
%sel = select i1 %cmp, i8 %x, i8 -128
@@ -14,9 +12,7 @@ define i8 @smax_min_limit(i8 %x) {
define i8 @smin_max_limit(i8 %x) {
; CHECK-LABEL: @smin_max_limit(
-; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 127
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[X]], i8 127
-; CHECK-NEXT: ret i8 [[SEL]]
+; CHECK-NEXT: ret i8 [[X:%.*]]
;
%cmp = icmp slt i8 %x, 127
%sel = select i1 %cmp, i8 %x, i8 127
@@ -25,9 +21,7 @@ define i8 @smin_max_limit(i8 %x) {
define <2 x i8> @umax_min_limit(<2 x i8> %x) {
; CHECK-LABEL: @umax_min_limit(
-; CHECK-NEXT: [[CMP:%.*]] = icmp ugt <2 x i8> [[X:%.*]], zeroinitializer
-; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> [[CMP]], <2 x i8> [[X]], <2 x i8> zeroinitializer
-; CHECK-NEXT: ret <2 x i8> [[SEL]]
+; CHECK-NEXT: ret <2 x i8> [[X:%.*]]
;
%cmp = icmp ugt <2 x i8> %x, zeroinitializer
%sel = select <2 x i1> %cmp, <2 x i8> %x, <2 x i8> zeroinitializer
@@ -36,15 +30,15 @@ define <2 x i8> @umax_min_limit(<2 x i8> %x) {
define i8 @umin_max_limit(i8 %x) {
; CHECK-LABEL: @umin_max_limit(
-; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[X:%.*]], -1
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i8 [[X]], i8 -1
-; CHECK-NEXT: ret i8 [[SEL]]
+; CHECK-NEXT: ret i8 [[X:%.*]]
;
%cmp = icmp ult i8 %x, 255
%sel = select i1 %cmp, i8 %x, i8 255
ret i8 %sel
}
+; negative test - wrong limit
+
define i8 @smax_not_min_limit(i8 %x) {
; CHECK-LABEL: @smax_not_min_limit(
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[X:%.*]], -127
@@ -56,6 +50,8 @@ define i8 @smax_not_min_limit(i8 %x) {
ret i8 %sel
}
+; negative test - wrong limit
+
define i8 @smin_not_min_limit(i8 %x) {
; CHECK-LABEL: @smin_not_min_limit(
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
More information about the llvm-branch-commits
mailing list