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llvm-project/llvm/test/CodeGen/ARM/2014-08-04-muls-it.ll

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ARM: correct isPredicable for MULS in ThHUMB mode The ARM ARM states that CPSR may not be updated by a MUL in thumb mode. Due to an ordering of Thumb 2 Size Reduction and If Conversion, we would end up generating a THUMB MULS inside an IT block. The If Conversion pass uses the TTI isPredicable method to ensure that it can transform a Basic Block. However, because we only check for IT handling on Thumb2 functions, we may miss some cases. Even then, it only validates that the CPSR is not *live* rather than it is not accessed. This corrects the handling for that particular case since the same restriction does not hold on the vast majority of the instructions. This does prevent the IfConversion optimization from kicking in in certain cases, but generating correct code is more valuable. Addresses PR20555. llvm-svn: 215328
2014-08-11 06:20:37 +08:00
; RUN: llc -mtriple thumbv7-eabi -arm-restrict-it -filetype asm -o - %s \
; RUN: | FileCheck %s
define arm_aapcscc i32 @function(i32 %i, i32 %j) {
entry:
%cmp = icmp eq i32 %i, %j
br i1 %cmp, label %if.then, label %if.end
if.then: ; preds = %entry
%mul = mul nsw i32 %i, %i
br label %if.end
if.end: ; preds = %if.then, %entry
%i.addr.0 = phi i32 [ %mul, %if.then ], [ %i, %entry ]
ret i32 %i.addr.0
}
; CHECK-LABEL: function
[ARM] Comply with rules on ARMv8-A thumb mode partial deprecation of IT. Summary: When identifing instructions that can be folded into a MOVCC instruction, checking for a predicate operand is not enough, also need to check for thumb2 function, with restrict-IT, is the machine instruction eligible for ARMv8 IT or not. Notes in ARMv8-A Architecture Reference Manual, section "Partial deprecation of IT" https://usermanual.wiki/Pdf/ARM20Architecture20Reference20ManualARMv8.1667877052.pdf "ARMv8-A deprecates some uses of the T32 IT instruction. All uses of IT that apply to instructions other than a single subsequent 16-bit instruction from a restricted set are deprecated, as are explicit references to the PC within that single 16-bit instruction. This permits the non-deprecated forms of IT and subsequent instructions to be treated as a single 32-bit conditional instruction." Reviewers: efriedma, lebedev.ri, t.p.northover, jmolloy, aemerson, compnerd, stoklund, ostannard Reviewed By: ostannard Subscribers: ostannard, javed.absar, kristof.beyls, hiraditya, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D63474 llvm-svn: 363739
2019-06-19 04:55:09 +08:00
; CHECK: mul r2, r0, r0
ARM: correct isPredicable for MULS in ThHUMB mode The ARM ARM states that CPSR may not be updated by a MUL in thumb mode. Due to an ordering of Thumb 2 Size Reduction and If Conversion, we would end up generating a THUMB MULS inside an IT block. The If Conversion pass uses the TTI isPredicable method to ensure that it can transform a Basic Block. However, because we only check for IT handling on Thumb2 functions, we may miss some cases. Even then, it only validates that the CPSR is not *live* rather than it is not accessed. This corrects the handling for that particular case since the same restriction does not hold on the vast majority of the instructions. This does prevent the IfConversion optimization from kicking in in certain cases, but generating correct code is more valuable. Addresses PR20555. llvm-svn: 215328
2014-08-11 06:20:37 +08:00
; CHECK: cmp r0, r1
; CHECK-NOT: mulseq r0, r0, r0
[ARM] Comply with rules on ARMv8-A thumb mode partial deprecation of IT. Summary: When identifing instructions that can be folded into a MOVCC instruction, checking for a predicate operand is not enough, also need to check for thumb2 function, with restrict-IT, is the machine instruction eligible for ARMv8 IT or not. Notes in ARMv8-A Architecture Reference Manual, section "Partial deprecation of IT" https://usermanual.wiki/Pdf/ARM20Architecture20Reference20ManualARMv8.1667877052.pdf "ARMv8-A deprecates some uses of the T32 IT instruction. All uses of IT that apply to instructions other than a single subsequent 16-bit instruction from a restricted set are deprecated, as are explicit references to the PC within that single 16-bit instruction. This permits the non-deprecated forms of IT and subsequent instructions to be treated as a single 32-bit conditional instruction." Reviewers: efriedma, lebedev.ri, t.p.northover, jmolloy, aemerson, compnerd, stoklund, ostannard Reviewed By: ostannard Subscribers: ostannard, javed.absar, kristof.beyls, hiraditya, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D63474 llvm-svn: 363739
2019-06-19 04:55:09 +08:00
; CHECK: moveq r0, r2
ARM: correct isPredicable for MULS in ThHUMB mode The ARM ARM states that CPSR may not be updated by a MUL in thumb mode. Due to an ordering of Thumb 2 Size Reduction and If Conversion, we would end up generating a THUMB MULS inside an IT block. The If Conversion pass uses the TTI isPredicable method to ensure that it can transform a Basic Block. However, because we only check for IT handling on Thumb2 functions, we may miss some cases. Even then, it only validates that the CPSR is not *live* rather than it is not accessed. This corrects the handling for that particular case since the same restriction does not hold on the vast majority of the instructions. This does prevent the IfConversion optimization from kicking in in certain cases, but generating correct code is more valuable. Addresses PR20555. llvm-svn: 215328
2014-08-11 06:20:37 +08:00
; CHECK: bx lr