[AArch64] Protect against overflowing shift amounts in performSETCCCombine

In the attached test case we can get into positions where the shift gets a
constant shift amount that is negative or larger than the bitwidth, leading to
trying to create an invalid constant. Add a check to make sure we can handle it
without assertions.

Fixes #60530

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 51b2236..fa1af5e 100644 (file)
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -20364,6 +20364,7 @@ static SDValue performSETCCCombine(SDNode *N,
   // setcc (srl x, imm), 0, ne ==> setcc (and x, (-1 << imm)), 0, ne
   if (Cond == ISD::SETNE && isNullConstant(RHS) &&
       LHS->getOpcode() == ISD::SRL && isa<ConstantSDNode>(LHS->getOperand(1)) &&
+      LHS->getConstantOperandVal(1) < VT.getScalarSizeInBits() &&
       LHS->hasOneUse()) {
     EVT TstVT = LHS->getValueType(0);
     if (TstVT.isScalarInteger() && TstVT.getFixedSizeInBits() <= 64) {

diff --git a/llvm/test/CodeGen/AArch64/arm64-xaluo.ll b/llvm/test/CodeGen/AArch64/arm64-xaluo.ll
index d2ba50c..118aca7 100644 (file)
--- a/llvm/test/CodeGen/AArch64/arm64-xaluo.ll
+++ b/llvm/test/CodeGen/AArch64/arm64-xaluo.ll
@@ -2618,6 +2618,35 @@ continue:
   ret i1 true
 }
 
+define i8 @pr60530() {
+; SDAG-LABEL: pr60530:
+; SDAG:       // %bb.0:
+; SDAG-NEXT:    mov w0, #-1
+; SDAG-NEXT:    ret
+;
+; FAST-LABEL: pr60530:
+; FAST:       // %bb.0:
+; FAST-NEXT:    mov w0, #-1
+; FAST-NEXT:    ret
+;
+; GISEL-LABEL: pr60530:
+; GISEL:       // %bb.0:
+; GISEL-NEXT:    mov w8, #1
+; GISEL-NEXT:    sbfx w0, w8, #0, #1
+; GISEL-NEXT:    ret
+  %1 = call { i8, i1 } @llvm.uadd.with.overflow.i8(i8 0, i8 1)
+  %2 = extractvalue { i8, i1 } %1, 1
+  %3 = zext i1 %2 to i8
+  %4 = shl i8 -1, %3
+  %5 = lshr i8 1, %4
+  %6 = icmp uge i8 %5, 1
+  %7 = sext i1 %6 to i8
+  %8 = zext i1 %2 to i8
+  %9 = icmp uge i8 %7, %8
+  %10 = sext i1 %9 to i8
+  ret i8 %10
+}
+
 declare {i8, i1} @llvm.sadd.with.overflow.i8(i8, i8) nounwind readnone
 declare {i16, i1} @llvm.sadd.with.overflow.i16(i16, i16) nounwind readnone
 declare {i32, i1} @llvm.sadd.with.overflow.i32(i32, i32) nounwind readnone