[RISCV] Check the types are the same for folding (sub 0, (setcc x, 0, setlt)) to (sra x, xlen - 1) #158179
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… setlt)) to (sra x, xlen - 1) We should check the type of x is the same as `sub` operation. Otherwise the shift amount xlen -1 will exceed the bit size of x. Fixes llvm#158121.
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@llvm/pr-subscribers-backend-risc-v Author: Jim Lin (tclin914) ChangesWe should check the type of x is the same as Fixes #158121. Full diff: https://github.com/llvm/llvm-project/pull/158179.diff 2 Files Affected:
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index ae9e2fef88673..0203d1a701147 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -15830,7 +15830,8 @@ static SDValue performSUBCombine(SDNode *N, SelectionDAG &DAG,
SDValue N1 = N->getOperand(1);
// fold (sub 0, (setcc x, 0, setlt)) -> (sra x, xlen - 1)
if (isNullConstant(N0) && N1.getOpcode() == ISD::SETCC && N1.hasOneUse() &&
- isNullConstant(N1.getOperand(1))) {
+ isNullConstant(N1.getOperand(1)) &&
+ N1.getValueType() == N1.getOperand(0).getValueType()) {
ISD::CondCode CCVal = cast<CondCodeSDNode>(N1.getOperand(2))->get();
if (CCVal == ISD::SETLT) {
SDLoc DL(N);
diff --git a/llvm/test/CodeGen/RISCV/pr158121.ll b/llvm/test/CodeGen/RISCV/pr158121.ll
new file mode 100644
index 0000000000000..2c018444e9c67
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/pr158121.ll
@@ -0,0 +1,17 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s -mtriple=riscv64 | FileCheck %s
+
+define i64 @f(ptr %p) {
+; CHECK-LABEL: f:
+; CHECK: # %bb.0:
+; CHECK-NEXT: lb a0, 0(a0)
+; CHECK-NEXT: srai a0, a0, 63
+; CHECK-NEXT: ret
+ %load = load i8, ptr %p, align 1
+ %conv1 = zext i8 %load to i32
+ %cmp = icmp ult i32 127, %conv1
+ %conv2 = zext i1 %cmp to i32
+ %sub = sub nsw i32 0, %conv2
+ %conv3 = sext i32 %sub to i64
+ ret i64 %conv3
+}
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/186/builds/12402 Here is the relevant piece of the build log for the reference |
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We should check the type of x is the same as
suboperation. Otherwise the shift amount xlen -1 will exceed the bit size of x.Fixes #158121.