[llvm] a22282b - [InstCombine] make icmp vector canonicalization safe for constant with undef elements
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 29 07:58:21 PDT 2019
Author: Sanjay Patel
Date: 2019-10-29T10:58:14-04:00
New Revision: a22282be54b309ce7ab0e6bf8595893384971646
URL: https://github.com/llvm/llvm-project/commit/a22282be54b309ce7ab0e6bf8595893384971646
DIFF: https://github.com/llvm/llvm-project/commit/a22282be54b309ce7ab0e6bf8595893384971646.diff
LOG: [InstCombine] make icmp vector canonicalization safe for constant with undef elements
This is a fix for:
https://bugs.llvm.org/show_bug.cgi?id=43730
...and as shown there, we have existing test cases that show potential miscompiles.
We could just bail out for vector constants that contain any undef elements, or we can do as shown here:
allow the transform, but replace the undefs with a safe value.
For most of the tests shown, this results in a full splat constant (no undefs) which is probably a win
for further IR analysis because we conservatively don't match undefs in most cases. Codegen can probably
recover these kinds of undef lanes via demanded elements analysis if that's profitable.
Differential Revision: https://reviews.llvm.org/D69519
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-eq-to-icmp-ule.ll
llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sge-to-icmp-sle.ll
llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll
llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-uge-to-icmp-ule.ll
llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ule-to-icmp-ule.ll
llvm/test/Transforms/InstCombine/icmp-vec.ll
llvm/test/Transforms/InstCombine/reuse-constant-from-select-in-icmp.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index a9f64feb600c..5fb3ec875713 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -5167,6 +5167,7 @@ llvm::getFlippedStrictnessPredicateAndConstant(CmpInst::Predicate Pred,
return WillIncrement ? !C->isMaxValue(IsSigned) : !C->isMinValue(IsSigned);
};
+ Constant *SafeReplacementConstant = nullptr;
if (auto *CI = dyn_cast<ConstantInt>(C)) {
// Bail out if the constant can't be safely incremented/decremented.
if (!ConstantIsOk(CI))
@@ -5186,12 +5187,23 @@ llvm::getFlippedStrictnessPredicateAndConstant(CmpInst::Predicate Pred,
auto *CI = dyn_cast<ConstantInt>(Elt);
if (!CI || !ConstantIsOk(CI))
return llvm::None;
+
+ if (!SafeReplacementConstant)
+ SafeReplacementConstant = CI;
}
} else {
// ConstantExpr?
return llvm::None;
}
+ // It may not be safe to change a compare predicate in the presence of
+ // undefined elements, so replace those elements with the first safe constant
+ // that we found.
+ if (C->containsUndefElement()) {
+ assert(SafeReplacementConstant && "Replacement constant not set");
+ C = Constant::replaceUndefsWith(C, SafeReplacementConstant);
+ }
+
CmpInst::Predicate NewPred = CmpInst::getFlippedStrictnessPredicate(Pred);
// Increment or decrement the constant.
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-eq-to-icmp-ule.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-eq-to-icmp-ule.ll
index bb304d7fa961..6a3564eb798b 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-eq-to-icmp-ule.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-eq-to-icmp-ule.ll
@@ -82,7 +82,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase1(<2 x i8> %x) {
define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
; CHECK-LABEL: @p3_vec_splat_undef(
-; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <3 x i8> [[X:%.*]], <i8 4, i8 undef, i8 4>
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <3 x i8> [[X:%.*]], <i8 4, i8 4, i8 4>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sge-to-icmp-sle.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sge-to-icmp-sle.ll
index 3ed42e415c23..3bfb48f41fe4 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sge-to-icmp-sle.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sge-to-icmp-sle.ll
@@ -61,7 +61,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase(<2 x i8> %x) {
define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
; CHECK-LABEL: @p3_vec_splat_undef(
-; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <3 x i8> [[X:%.*]], <i8 4, i8 undef, i8 4>
+; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <3 x i8> [[X:%.*]], <i8 4, i8 4, i8 4>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll
index 64be961e5267..eec8bdc097b9 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-sle-to-icmp-sle.ll
@@ -76,7 +76,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase() {
define <3 x i1> @p3_vec_splat_undef() {
; CHECK-LABEL: @p3_vec_splat_undef(
; CHECK-NEXT: [[X:%.*]] = call <3 x i8> @gen3x8()
-; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <3 x i8> [[X]], <i8 4, i8 undef, i8 4>
+; CHECK-NEXT: [[TMP1:%.*]] = icmp slt <3 x i8> [[X]], <i8 4, i8 4, i8 4>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%x = call <3 x i8> @gen3x8()
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-uge-to-icmp-ule.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-uge-to-icmp-ule.ll
index 18325ed17599..1ae84cf8144e 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-uge-to-icmp-ule.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-uge-to-icmp-ule.ll
@@ -82,7 +82,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase1(<2 x i8> %x) {
define <3 x i1> @p3_vec_splat_undef(<3 x i8> %x) {
; CHECK-LABEL: @p3_vec_splat_undef(
-; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <3 x i8> [[X:%.*]], <i8 4, i8 undef, i8 4>
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <3 x i8> [[X:%.*]], <i8 4, i8 4, i8 4>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%tmp0 = and <3 x i8> %x, <i8 3, i8 undef, i8 3>
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ule-to-icmp-ule.ll b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ule-to-icmp-ule.ll
index 6f267206dbe8..2d2bfce73b72 100644
--- a/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ule-to-icmp-ule.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-constant-low-bit-mask-and-icmp-ule-to-icmp-ule.ll
@@ -99,7 +99,7 @@ define <2 x i1> @p2_vec_nonsplat_edgecase1() {
define <3 x i1> @p3_vec_splat_undef() {
; CHECK-LABEL: @p3_vec_splat_undef(
; CHECK-NEXT: [[X:%.*]] = call <3 x i8> @gen3x8()
-; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <3 x i8> [[X]], <i8 4, i8 undef, i8 4>
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ult <3 x i8> [[X]], <i8 4, i8 4, i8 4>
; CHECK-NEXT: ret <3 x i1> [[TMP1]]
;
%x = call <3 x i8> @gen3x8()
diff --git a/llvm/test/Transforms/InstCombine/icmp-vec.ll b/llvm/test/Transforms/InstCombine/icmp-vec.ll
index da80450ca9dc..8f4cfdbe9da5 100644
--- a/llvm/test/Transforms/InstCombine/icmp-vec.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-vec.ll
@@ -181,7 +181,7 @@ define <2 x i1> @PR27756_1(<2 x i8> %a) {
define <3 x i1> @PR27756_2(<3 x i8> %a) {
; CHECK-LABEL: @PR27756_2(
-; CHECK-NEXT: [[CMP:%.*]] = icmp slt <3 x i8> [[A:%.*]], <i8 43, i8 undef, i8 1>
+; CHECK-NEXT: [[CMP:%.*]] = icmp slt <3 x i8> [[A:%.*]], <i8 43, i8 43, i8 1>
; CHECK-NEXT: ret <3 x i1> [[CMP]]
;
%cmp = icmp sle <3 x i8> %a, <i8 42, i8 undef, i8 0>
@@ -190,7 +190,7 @@ define <3 x i1> @PR27756_2(<3 x i8> %a) {
define <3 x i1> @PR27756_3(<3 x i8> %a) {
; CHECK-LABEL: @PR27756_3(
-; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <3 x i8> [[A:%.*]], <i8 undef, i8 0, i8 41>
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <3 x i8> [[A:%.*]], <i8 0, i8 0, i8 41>
; CHECK-NEXT: ret <3 x i1> [[CMP]]
;
%cmp = icmp sge <3 x i8> %a, <i8 undef, i8 1, i8 42>
diff --git a/llvm/test/Transforms/InstCombine/reuse-constant-from-select-in-icmp.ll b/llvm/test/Transforms/InstCombine/reuse-constant-from-select-in-icmp.ll
index 057ae8640b2c..6eb21466e603 100644
--- a/llvm/test/Transforms/InstCombine/reuse-constant-from-select-in-icmp.ll
+++ b/llvm/test/Transforms/InstCombine/reuse-constant-from-select-in-icmp.ll
@@ -106,7 +106,7 @@ define <2 x i32> @p7_vec_splat_sgt(<2 x i32> %x, <2 x i32> %y) {
define <2 x i32> @p8_vec_nonsplat_undef0(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @p8_vec_nonsplat_undef0(
-; CHECK-NEXT: [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 undef>
+; CHECK-NEXT: [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 65535>
; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 65535>, <2 x i32> [[Y:%.*]]
; CHECK-NEXT: ret <2 x i32> [[R]]
;
@@ -126,7 +126,7 @@ define <2 x i32> @p9_vec_nonsplat_undef1(<2 x i32> %x, <2 x i32> %y) {
}
define <2 x i32> @p10_vec_nonsplat_undef2(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @p10_vec_nonsplat_undef2(
-; CHECK-NEXT: [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 undef>
+; CHECK-NEXT: [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 65535>
; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 undef>, <2 x i32> [[Y:%.*]]
; CHECK-NEXT: ret <2 x i32> [[R]]
;
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