release/19.x: [SCEV] Fix sext handling for getConstantMultiple (#117093)
#117136
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@antoniofrighetto What do you think about merging this PR to the release branch? |
llvmbot
added
llvm:analysis
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@llvm/pr-subscribers-llvm-transforms Author: None (llvmbot) ChangesBackport 458dfbd Requested by: @dtcxzyw Full diff: https://github.com/llvm/llvm-project/pull/117136.diff 3 Files Affected:
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 51cffac8087689..412cfe73d3e559 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -6313,8 +6313,10 @@ APInt ScalarEvolution::getConstantMultipleImpl(const SCEV *S) {
return getConstantMultiple(Z->getOperand()).zext(BitWidth);
}
case scSignExtend: {
+ // Only multiples that are a power of 2 will hold after sext.
const SCEVSignExtendExpr *E = cast<SCEVSignExtendExpr>(S);
- return getConstantMultiple(E->getOperand()).sext(BitWidth);
+ uint32_t TZ = getMinTrailingZeros(E->getOperand());
+ return GetShiftedByZeros(TZ);
}
case scMulExpr: {
const SCEVMulExpr *M = cast<SCEVMulExpr>(S);
diff --git a/llvm/test/Analysis/ScalarEvolution/pr116483.ll b/llvm/test/Analysis/ScalarEvolution/pr116483.ll
new file mode 100644
index 00000000000000..cc2334e9c64f92
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/pr116483.ll
@@ -0,0 +1,26 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -disable-output "-passes=print<scalar-evolution>" < %s 2>&1 | FileCheck %s
+
+define i16 @test() {
+; CHECK-LABEL: 'test'
+; CHECK-NEXT: Classifying expressions for: @test
+; CHECK-NEXT: %xor = xor i32 0, 3
+; CHECK-NEXT: --> %xor U: [3,4) S: [3,4)
+; CHECK-NEXT: %mul = mul i32 %xor, 329
+; CHECK-NEXT: --> (329 * %xor)<nuw><nsw> U: [987,988) S: [987,988)
+; CHECK-NEXT: %conv = trunc i32 %mul to i16
+; CHECK-NEXT: --> (329 * (trunc i32 %xor to i16))<nuw><nsw> U: [987,988) S: [987,988)
+; CHECK-NEXT: %sext = shl i16 %conv, 8
+; CHECK-NEXT: --> (18688 * (trunc i32 %xor to i16))<nuw> U: [-9472,-9471) S: [-9472,-9471)
+; CHECK-NEXT: %conv1 = ashr i16 %sext, 8
+; CHECK-NEXT: --> (sext i8 (73 * (trunc i32 %xor to i8))<nuw> to i16) U: [-37,-36) S: [-37,-36)
+; CHECK-NEXT: Determining loop execution counts for: @test
+;
+entry:
+ %xor = xor i32 0, 3
+ %mul = mul i32 %xor, 329
+ %conv = trunc i32 %mul to i16
+ %sext = shl i16 %conv, 8
+ %conv1 = ashr i16 %sext, 8
+ ret i16 %conv1
+}
diff --git a/llvm/test/Transforms/IndVarSimplify/pr116483.ll b/llvm/test/Transforms/IndVarSimplify/pr116483.ll
new file mode 100644
index 00000000000000..ae108a525223e0
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/pr116483.ll
@@ -0,0 +1,36 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=indvars < %s | FileCheck %s
+
+define i32 @test() {
+; CHECK-LABEL: define i32 @test() {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[XOR:%.*]] = xor i32 0, 3
+; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[XOR]], 329
+; CHECK-NEXT: [[CONV:%.*]] = trunc i32 [[MUL]] to i16
+; CHECK-NEXT: [[SEXT:%.*]] = shl i16 [[CONV]], 8
+; CHECK-NEXT: [[CONV1:%.*]] = ashr i16 [[SEXT]], 8
+; CHECK-NEXT: br label %[[LOOP_BODY:.*]]
+; CHECK: [[LOOP_BODY]]:
+; CHECK-NEXT: br i1 true, label %[[EXIT:.*]], label %[[LOOP_BODY]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: [[CONV3:%.*]] = zext i16 [[CONV1]] to i32
+; CHECK-NEXT: ret i32 [[CONV3]]
+;
+entry:
+ %xor = xor i32 0, 3
+ %mul = mul i32 %xor, 329
+ %conv = trunc i32 %mul to i16
+ %sext = shl i16 %conv, 8
+ %conv1 = ashr i16 %sext, 8
+ %conv3 = zext i16 %conv1 to i32
+ br label %loop.body
+
+loop.body:
+ %indvar = phi i32 [ %indvar.inc, %loop.body ], [ 1, %entry ]
+ %indvar.inc = add nuw i32 %indvar, 1
+ %exitcond = icmp eq i32 %indvar, %conv3
+ br i1 %exitcond, label %exit, label %loop.body
+
+exit:
+ ret i32 %conv3
+}
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@llvm/pr-subscribers-llvm-analysis Author: None (llvmbot) ChangesBackport 458dfbd Requested by: @dtcxzyw Full diff: https://github.com/llvm/llvm-project/pull/117136.diff 3 Files Affected:
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 51cffac8087689..412cfe73d3e559 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -6313,8 +6313,10 @@ APInt ScalarEvolution::getConstantMultipleImpl(const SCEV *S) {
return getConstantMultiple(Z->getOperand()).zext(BitWidth);
}
case scSignExtend: {
+ // Only multiples that are a power of 2 will hold after sext.
const SCEVSignExtendExpr *E = cast<SCEVSignExtendExpr>(S);
- return getConstantMultiple(E->getOperand()).sext(BitWidth);
+ uint32_t TZ = getMinTrailingZeros(E->getOperand());
+ return GetShiftedByZeros(TZ);
}
case scMulExpr: {
const SCEVMulExpr *M = cast<SCEVMulExpr>(S);
diff --git a/llvm/test/Analysis/ScalarEvolution/pr116483.ll b/llvm/test/Analysis/ScalarEvolution/pr116483.ll
new file mode 100644
index 00000000000000..cc2334e9c64f92
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/pr116483.ll
@@ -0,0 +1,26 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -disable-output "-passes=print<scalar-evolution>" < %s 2>&1 | FileCheck %s
+
+define i16 @test() {
+; CHECK-LABEL: 'test'
+; CHECK-NEXT: Classifying expressions for: @test
+; CHECK-NEXT: %xor = xor i32 0, 3
+; CHECK-NEXT: --> %xor U: [3,4) S: [3,4)
+; CHECK-NEXT: %mul = mul i32 %xor, 329
+; CHECK-NEXT: --> (329 * %xor)<nuw><nsw> U: [987,988) S: [987,988)
+; CHECK-NEXT: %conv = trunc i32 %mul to i16
+; CHECK-NEXT: --> (329 * (trunc i32 %xor to i16))<nuw><nsw> U: [987,988) S: [987,988)
+; CHECK-NEXT: %sext = shl i16 %conv, 8
+; CHECK-NEXT: --> (18688 * (trunc i32 %xor to i16))<nuw> U: [-9472,-9471) S: [-9472,-9471)
+; CHECK-NEXT: %conv1 = ashr i16 %sext, 8
+; CHECK-NEXT: --> (sext i8 (73 * (trunc i32 %xor to i8))<nuw> to i16) U: [-37,-36) S: [-37,-36)
+; CHECK-NEXT: Determining loop execution counts for: @test
+;
+entry:
+ %xor = xor i32 0, 3
+ %mul = mul i32 %xor, 329
+ %conv = trunc i32 %mul to i16
+ %sext = shl i16 %conv, 8
+ %conv1 = ashr i16 %sext, 8
+ ret i16 %conv1
+}
diff --git a/llvm/test/Transforms/IndVarSimplify/pr116483.ll b/llvm/test/Transforms/IndVarSimplify/pr116483.ll
new file mode 100644
index 00000000000000..ae108a525223e0
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/pr116483.ll
@@ -0,0 +1,36 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=indvars < %s | FileCheck %s
+
+define i32 @test() {
+; CHECK-LABEL: define i32 @test() {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[XOR:%.*]] = xor i32 0, 3
+; CHECK-NEXT: [[MUL:%.*]] = mul i32 [[XOR]], 329
+; CHECK-NEXT: [[CONV:%.*]] = trunc i32 [[MUL]] to i16
+; CHECK-NEXT: [[SEXT:%.*]] = shl i16 [[CONV]], 8
+; CHECK-NEXT: [[CONV1:%.*]] = ashr i16 [[SEXT]], 8
+; CHECK-NEXT: br label %[[LOOP_BODY:.*]]
+; CHECK: [[LOOP_BODY]]:
+; CHECK-NEXT: br i1 true, label %[[EXIT:.*]], label %[[LOOP_BODY]]
+; CHECK: [[EXIT]]:
+; CHECK-NEXT: [[CONV3:%.*]] = zext i16 [[CONV1]] to i32
+; CHECK-NEXT: ret i32 [[CONV3]]
+;
+entry:
+ %xor = xor i32 0, 3
+ %mul = mul i32 %xor, 329
+ %conv = trunc i32 %mul to i16
+ %sext = shl i16 %conv, 8
+ %conv1 = ashr i16 %sext, 8
+ %conv3 = zext i16 %conv1 to i32
+ br label %loop.body
+
+loop.body:
+ %indvar = phi i32 [ %indvar.inc, %loop.body ], [ 1, %entry ]
+ %indvar.inc = add nuw i32 %indvar, 1
+ %exitcond = icmp eq i32 %indvar, %conv3
+ br i1 %exitcond, label %exit, label %loop.body
+
+exit:
+ ret i32 %conv3
+}
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nikic
approved these changes
Nov 21, 2024
Counterexample: 219 is a multiple of 73. But `sext i8 219 to i16 = 65499` is not. Fixes llvm#116483. (cherry picked from commit 458dfbd)
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@dtcxzyw (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR. |
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Backport 458dfbd
Requested by: @dtcxzyw