[X86][DAGCombiner] Fix assertion failure in combinei64TruncSrlAdd

[dtcxzyw]

Closes #128158.

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: Yingwei Zheng (dtcxzyw)

Changes

Closes #128158.

---

Full diff: https://github.com/llvm/llvm-project/pull/128194.diff

2 Files Affected:

• (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+1-1)
• (modified) llvm/test/CodeGen/X86/combine-i64-trunc-srl-add.ll (+28)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 683c8c3bdf96d..57ce634607dc5 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -53713,7 +53713,7 @@ static SDValue combinei64TruncSrlAdd(SDValue N, EVT VT, SelectionDAG &DAG,
                                  m_ConstInt(SrlConst)))))
     return SDValue();
 
-  if (SrlConst.ule(31) || AddConst.lshr(SrlConst).shl(SrlConst) != AddConst)
+  if (SrlConst.ule(32) || AddConst.lshr(SrlConst).shl(SrlConst) != AddConst)
     return SDValue();
 
   SDValue AddLHSSrl =
diff --git a/llvm/test/CodeGen/X86/combine-i64-trunc-srl-add.ll b/llvm/test/CodeGen/X86/combine-i64-trunc-srl-add.ll
index 1ce1e7e1c2b9f..41e1a24b239a6 100644
--- a/llvm/test/CodeGen/X86/combine-i64-trunc-srl-add.ll
+++ b/llvm/test/CodeGen/X86/combine-i64-trunc-srl-add.ll
@@ -123,3 +123,31 @@ define i32 @test_trunc_add(i64 %x) {
   %conv = trunc i64 %shr to i32
   ret i32 %conv
 }
+
+; Make sure we don't crash on this test case.
+
+define i32 @pr128158(i64 %x) {
+; X64-LABEL: pr128158:
+; X64:       # %bb.0: # %entry
+; X64-NEXT:    movabsq $-4294967296, %rax # imm = 0xFFFFFFFF00000000
+; X64-NEXT:    addq %rdi, %rax
+; X64-NEXT:    shrq $32, %rax
+; X64-NEXT:    .p2align 4
+; X64-NEXT:  .LBB9_1: # %for.body
+; X64-NEXT:    # =>This Inner Loop Header: Depth=1
+; X64-NEXT:    cmpl $9, %eax
+; X64-NEXT:    jb .LBB9_1
+; X64-NEXT:  # %bb.2: # %exit
+; X64-NEXT:    xorl %eax, %eax
+; X64-NEXT:    retq
+entry:
+  br label %for.body
+
+for.body:
+  %add = add i64 %x, -4294967296
+  %cmp = icmp ult i64 %add, 38654705664
+  br i1 %cmp, label %for.body, label %exit
+
+exit:
+  ret i32 0
+}