[X86] LowerAsmOperandForConstraint - ensure we treat L constraint immediates as signed constants (#171098)

getTargetConstant no longer tolerates sign-extended values that can't be
represented by the appropriate APInt bitwidth, which defaults to
unsigned behaviour.

Fixes #166058

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -61974,8 +61974,8 @@ void X86TargetLowering::LowerAsmOperandForConstraint(SDValue Op,
     if (auto *C = dyn_cast<ConstantSDNode>(Op)) {
       if (C->getZExtValue() == 0xff || C->getZExtValue() == 0xffff ||
           (Subtarget.is64Bit() && C->getZExtValue() == 0xffffffff)) {
-        Result = DAG.getTargetConstant(C->getSExtValue(), SDLoc(Op),
-                                       Op.getValueType());
+        Result = DAG.getSignedTargetConstant(C->getSExtValue(), SDLoc(Op),
+                                             Op.getValueType());
         break;
       }
     }
@@ -62013,7 +62013,8 @@ void X86TargetLowering::LowerAsmOperandForConstraint(SDValue Op,
       if (ConstantInt::isValueValidForType(Type::getInt32Ty(*DAG.getContext()),
                                            C->getSExtValue())) {
         // Widen to 64 bits here to get it sign extended.
-        Result = DAG.getTargetConstant(C->getSExtValue(), SDLoc(Op), MVT::i64);
+        Result =
+            DAG.getSignedTargetConstant(C->getSExtValue(), SDLoc(Op), MVT::i64);
         break;
       }
     // FIXME gcc accepts some relocatable values here too, but only in certain
@@ -62062,9 +62063,11 @@ void X86TargetLowering::LowerAsmOperandForConstraint(SDValue Op,
       BooleanContent BCont = getBooleanContents(MVT::i64);
       ISD::NodeType ExtOpc = IsBool ? getExtendForContent(BCont)
                                     : ISD::SIGN_EXTEND;
-      int64_t ExtVal = ExtOpc == ISD::ZERO_EXTEND ? CST->getZExtValue()
-                                                  : CST->getSExtValue();
-      Result = DAG.getTargetConstant(ExtVal, SDLoc(Op), MVT::i64);
+      SDLoc DL(Op);
+      Result =
+          ExtOpc == ISD::ZERO_EXTEND
+              ? DAG.getTargetConstant(CST->getZExtValue(), DL, MVT::i64)
+              : DAG.getSignedTargetConstant(CST->getSExtValue(), DL, MVT::i64);
       break;
     }
 

llvm/test/CodeGen/X86/pr166058.ll

@@ -0,0 +1,15 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
+; RUN: llc < %s -mtriple=x86_64-- | FileCheck %s
+
+@out = global i32 0, align 4
+define void @bar() {
+; CHECK-LABEL: bar:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movq out@GOTPCREL(%rip), %rax
+; CHECK-NEXT:    #APP
+; CHECK-NEXT:    addl $-1, (%rax)
+; CHECK-NEXT:    #NO_APP
+; CHECK-NEXT:    retq
+  call void asm "addl $1,$0", "=*m,L,~{dirflag},~{fpsr},~{flags}"(ptr elementtype(i32) @out, i32 -1)
+  ret void
+}