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[X86] Fix a bug with fetch_add(INT32_MIN)
Summary: Fix pr21099 The pseudocode of what we were doing (spread through two functions) was: if (operand.doesNotFitIn32Bits()) Opc.initializeWithFoo(); if (operand < 0) operand = -operand; if (operand.doesFitIn8Bits()) Opc.initializeWithBar(); else if (operand.doesFitIn32Bits()) Opc.initializeWithBlah(); doStuff(Opc); So for operand == INT32_MIN, Opc was never initialized because the operand changes from fitting in 32 bits to not fitting, causing the various bugs/error messages noted by pr21099. This patch adds an extra test at the beginning for this case, and an llvm_unreachable to have better error message if the operand ends up not fitting in 32-bits at the end. Test Plan: new test + make check Reviewers: jfb Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D5655 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219257 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -34,6 +34,7 @@
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetOptions.h"
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#include <stdint.h>
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using namespace llvm;
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#define DEBUG_TYPE "x86-isel"
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@ -1712,6 +1713,12 @@ static SDValue getAtomicLoadArithTargetConstant(SelectionDAG *CurDAG,
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// Quit if not 32-bit imm.
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if ((int32_t)CNVal != CNVal)
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return Val;
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// Quit if INT32_MIN: it would be negated as it is negative and overflow,
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// producing an immediate that does not fit in the 32 bits available for
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// an immediate operand to sub. However, it still fits in 32 bits for the
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// add (since it is not negated) so we can return target-constant.
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if (CNVal == INT32_MIN)
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return CurDAG->getTargetConstant(CNVal, NVT);
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// For atomic-load-add, we could do some optimizations.
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if (Op == ADD) {
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// Translate to INC/DEC if ADD by 1 or -1.
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@ -1824,6 +1831,8 @@ SDNode *X86DAGToDAGISel::SelectAtomicLoadArith(SDNode *Node, MVT NVT) {
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Opc = AtomicOpcTbl[Op][SextConstantI64];
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else if (i64immSExt32(Val.getNode()))
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Opc = AtomicOpcTbl[Op][ConstantI64];
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else
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llvm_unreachable("True 64 bits constant in SelectAtomicLoadArith");
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} else
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Opc = AtomicOpcTbl[Op][I64];
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break;
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10
test/CodeGen/X86/pr21099.ll
Normal file
10
test/CodeGen/X86/pr21099.ll
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@ -0,0 +1,10 @@
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; RUN: llc < %s -O2 -march=x86-64 -verify-machineinstrs | FileCheck %s
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define void @pr21099(i64* %p) {
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; CHECK-LABEL: pr21099
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; CHECK: lock
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; CHECK-NEXT: addq $-2147483648
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; This number is INT32_MIN: 0x80000000UL
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%1 = atomicrmw add i64* %p, i64 -2147483648 seq_cst
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ret void
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}
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