From: Lang Hames Date: Mon, 28 Oct 2013 20:51:11 +0000 (+0000) Subject: Return early from getUnconditionalBranchTargetOpValue if the branch target is X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3d478aee8e2480661cb0d98b10da8ad2ebf59fcf;p=llvm Return early from getUnconditionalBranchTargetOpValue if the branch target is an MCExpr, in order to avoid writing an encoded zero value in the immediate field. When getUnconditionalBranchTargetOpValue is called with an MCExpr target, we don't know what the final immediate field value should be. We shouldn't explicitly set the immediate field to an encoded zero value as zero is encoded with a non-zero bit pattern. This leads to bits being set that pollute the final immediate value. The nature of the encoding is such that the polluted bits only affect very large immediate values, explaining why this hasn't caused problems earlier. Fixes . git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193535 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp b/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp index e4c37276493..4382d0d9714 100644 --- a/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp +++ b/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp @@ -641,7 +641,7 @@ getUnconditionalBranchTargetOpValue(const MCInst &MI, unsigned OpIdx, const MCOperand MO = MI.getOperand(OpIdx); if(MO.isExpr()) - Val = ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_t2_uncondbranch, Fixups); + return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_t2_uncondbranch, Fixups); else Val = MO.getImm() >> 1; diff --git a/test/MC/ARM/basic-thumb2-instructions.s b/test/MC/ARM/basic-thumb2-instructions.s index fdb22252ab3..1954ba8299b 100644 --- a/test/MC/ARM/basic-thumb2-instructions.s +++ b/test/MC/ARM/basic-thumb2-instructions.s @@ -226,12 +226,12 @@ _func: beq.w _bar bmi.w #-183396 -@ CHECK: b.w _bar @ encoding: [A,0xf0'A',A,0xb8'A'] +@ CHECK: b.w _bar @ encoding: [A,0xf0'A',A,0x90'A'] @ fixup A - offset: 0, value: _bar, kind: fixup_t2_uncondbranch @ CHECK: beq.w _bar @ encoding: [A,0xf0'A',A,0x80'A'] @ fixup A - offset: 0, value: _bar, kind: fixup_t2_condbranch @ CHECK: it eq @ encoding: [0x08,0xbf] -@ CHECK: beq.w _bar @ encoding: [A,0xf0'A',A,0xb8'A'] +@ CHECK: beq.w _bar @ encoding: [A,0xf0'A',A,0x90'A'] @ fixup A - offset: 0, value: _bar, kind: fixup_t2_uncondbranch @ CHECK: bmi.w #-183396 @ encoding: [0x13,0xf5,0xce,0xa9]