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Fix PR5694. The CMN instructions set the flags differently from CMP, so they

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cannot be directly interchanged for comparisons against negated values.
Disable the CMN instructions for the time being.

llvm-svn: 94119
This commit is contained in:
Jim Grosbach 2010-01-22 00:08:13 +00:00
parent 30dee16eed
commit 231a0d01a9
5 changed files with 31 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
lib/Target/ARM/ARMInstrInfo.td
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@ -1539,8 +1539,10 @@ def : ARMV6Pat<(or (and GPR:$src1, 0xFFFF0000),
defm CMP : AI1_cmp_irs<0b1010, "cmp",
BinOpFrag<(ARMcmp node:$LHS, node:$RHS)>>;
defm CMN : AI1_cmp_irs<0b1011, "cmn",
BinOpFrag<(ARMcmp node:$LHS,(ineg node:$RHS))>>;
//FIXME: Disable CMN, as CCodes are backwards from compare expectations
// Compare-to-zero still works out, just not the relationals
//defm CMN : AI1_cmp_irs<0b1011, "cmn",
// BinOpFrag<(ARMcmp node:$LHS,(ineg node:$RHS))>>;
// Note that TST/TEQ don't set all the same flags that CMP does!
defm TST : AI1_cmp_irs<0b1000, "tst",
@ -1553,11 +1555,11 @@ defm CMPz : AI1_cmp_irs<0b1010, "cmp",
defm CMNz : AI1_cmp_irs<0b1011, "cmn",
BinOpFrag<(ARMcmpZ node:$LHS,(ineg node:$RHS))>>;
def : ARMPat<(ARMcmp GPR:$src, so_imm_neg:$imm),
(CMNri GPR:$src, so_imm_neg:$imm)>;
//def : ARMPat<(ARMcmp GPR:$src, so_imm_neg:$imm),
// (CMNri GPR:$src, so_imm_neg:$imm)>;
def : ARMPat<(ARMcmpZ GPR:$src, so_imm_neg:$imm),
(CMNri GPR:$src, so_imm_neg:$imm)>;
(CMNzri GPR:$src, so_imm_neg:$imm)>;
// Conditional moves

10
lib/Target/ARM/ARMInstrThumb.td
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@ -534,10 +534,12 @@ def tBIC : T1sIt<(outs tGPR:$dst), (ins tGPR:$lhs, tGPR:$rhs), IIC_iALUr,
// CMN register
let Defs = [CPSR] in {
def tCMN : T1pI<(outs), (ins tGPR:$lhs, tGPR:$rhs), IIC_iCMPr,
"cmn", "\t$lhs, $rhs",
[(ARMcmp tGPR:$lhs, (ineg tGPR:$rhs))]>,
T1DataProcessing<0b1011>;
//FIXME: Disable CMN, as CCodes are backwards from compare expectations
// Compare-to-zero still works out, just not the relationals
//def tCMN : T1pI<(outs), (ins tGPR:$lhs, tGPR:$rhs), IIC_iCMPr,
// "cmn", "\t$lhs, $rhs",
// [(ARMcmp tGPR:$lhs, (ineg tGPR:$rhs))]>,
// T1DataProcessing<0b1011>;
def tCMNz : T1pI<(outs), (ins tGPR:$lhs, tGPR:$rhs), IIC_iCMPr,
"cmn", "\t$lhs, $rhs",
[(ARMcmpZ tGPR:$lhs, (ineg tGPR:$rhs))]>,

12
lib/Target/ARM/ARMInstrThumb2.td
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@ -1609,16 +1609,18 @@ defm t2CMP : T2I_cmp_irs<0b1101, "cmp",
defm t2CMPz : T2I_cmp_irs<0b1101, "cmp",
BinOpFrag<(ARMcmpZ node:$LHS, node:$RHS)>>;
defm t2CMN : T2I_cmp_irs<0b1000, "cmn",
BinOpFrag<(ARMcmp node:$LHS,(ineg node:$RHS))>>;
//FIXME: Disable CMN, as CCodes are backwards from compare expectations
// Compare-to-zero still works out, just not the relationals
//defm t2CMN : T2I_cmp_irs<0b1000, "cmn",
// BinOpFrag<(ARMcmp node:$LHS,(ineg node:$RHS))>>;
defm t2CMNz : T2I_cmp_irs<0b1000, "cmn",
BinOpFrag<(ARMcmpZ node:$LHS,(ineg node:$RHS))>>;
def : T2Pat<(ARMcmp GPR:$src, t2_so_imm_neg:$imm),
(t2CMNri GPR:$src, t2_so_imm_neg:$imm)>;
//def : T2Pat<(ARMcmp GPR:$src, t2_so_imm_neg:$imm),
// (t2CMNri GPR:$src, t2_so_imm_neg:$imm)>;
def : T2Pat<(ARMcmpZ GPR:$src, t2_so_imm_neg:$imm),
(t2CMNri GPR:$src, t2_so_imm_neg:$imm)>;
(t2CMNzri GPR:$src, t2_so_imm_neg:$imm)>;
defm t2TST : T2I_cmp_irs<0b0000, "tst",
BinOpFrag<(ARMcmpZ (and node:$LHS, node:$RHS), 0)>>;

9
lib/Target/ARM/README.txt
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@ -596,3 +596,12 @@ Make use of the "rbit" instruction.
Take a look at test/CodeGen/Thumb2/machine-licm.ll. ARM should be taught how
to licm and cse the unnecessary load from cp#1.
//===---------------------------------------------------------------------===//
The CMN instruction sets the flags like an ADD instruction, while CMP sets
them like a subtract. Therefore to be able to use CMN for comparisons other
than the Z bit, we'll need additional logic to reverse the conditionals
associated with the comparison. Perhaps a pseudo-instruction for the comparison,
with a post-codegen pass to clean up and handle the condition codes?
See PR5694 for testcase.

3
lib/Target/ARM/Thumb2SizeReduction.cpp
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@ -65,7 +65,8 @@ namespace {
{ ARM::t2ASRri, ARM::tASRri, 0, 5, 0, 1, 0, 0,0, 0 },
{ ARM::t2ASRrr, 0, ARM::tASRrr, 0, 0, 0, 1, 0,0, 0 },
{ ARM::t2BICrr, 0, ARM::tBIC, 0, 0, 0, 1, 0,0, 0 },
{ ARM::t2CMNrr, ARM::tCMN, 0, 0, 0, 1, 0, 2,0, 0 },
//FIXME: Disable CMN, as CCodes are backwards from compare expectations
//{ ARM::t2CMNrr, ARM::tCMN, 0, 0, 0, 1, 0, 2,0, 0 },
{ ARM::t2CMPri, ARM::tCMPi8, 0, 8, 0, 1, 0, 2,0, 0 },
{ ARM::t2CMPrr, ARM::tCMPhir, 0, 0, 0, 0, 0, 2,0, 0 },
{ ARM::t2CMPzri,ARM::tCMPzi8, 0, 8, 0, 1, 0, 2,0, 0 },