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[MiSched] Fix a logic error in tryPressure() 

Fixes a logic error in the MachineScheduler found by Steve Montgomery (and
confirmed by Andy). This has gone unfixed for months because the fix has been
found to introduce some small performance regressions. However, Andy has
recommended that, at this point, we fix this to avoid further dependence on the
incorrect behavior (and then follow-up separately on any regressions), and I
agree.

Fixes PR18883.

llvm-svn: 219512
This commit is contained in:
Hal Finkel 2014-10-10 17:06:20 +00:00
parent 12f9488e33
commit 7a87f8a670
3 changed files with 7 additions and 5 deletions
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4
llvm/lib/CodeGen/MachineScheduler.cpp
View File

@ -2495,8 +2495,8 @@ static bool tryPressure(const PressureChange &TryP,
}
// If one candidate decreases and the other increases, go with it.
// Invalid candidates have UnitInc==0.
if (tryLess(TryP.getUnitInc() < 0, CandP.getUnitInc() < 0, TryCand, Cand,
Reason)) {
if (tryGreater(TryP.getUnitInc() < 0, CandP.getUnitInc() < 0, TryCand, Cand,
Reason)) {
return true;
}
// If the candidates are decreasing pressure, reverse priority.

2
llvm/test/CodeGen/X86/misched-matmul.ll
View File

@ -10,7 +10,7 @@
; more complex cases.
;
; CHECK: @wrap_mul4
; CHECK: 22 regalloc - Number of spills inserted
; CHECK: 23 regalloc - Number of spills inserted
define void @wrap_mul4(double* nocapture %Out, [4 x double]* nocapture %A, [4 x double]* nocapture %B) #0 {
entry:

6
llvm/test/CodeGen/X86/ragreedy-last-chance-recoloring.ll
View File

@ -2,10 +2,12 @@
; Without the last chance recoloring, this test fails with:
; "ran out of registers".
; RUN: not llc -regalloc=greedy -relocation-model=pic -lcr-max-depth=0 < %s 2>&1 | FileCheck %s --check-prefix=CHECK-DEPTH
; NOTE: With the fix to PR18883, we don't actually run out of registers here
; any more, and so those checks are disabled. This test remains only for general coverage.
; XXX: not llc -regalloc=greedy -relocation-model=pic -lcr-max-depth=0 < %s 2>&1 | FileCheck %s --check-prefix=CHECK-DEPTH
; Test whether failure due to cutoff for depth is reported
; RUN: not llc -regalloc=greedy -relocation-model=pic -lcr-max-interf=1 < %s 2>&1 | FileCheck %s --check-prefix=CHECK-INTERF
; XXX: not llc -regalloc=greedy -relocation-model=pic -lcr-max-interf=1 < %s 2>&1 | FileCheck %s --check-prefix=CHECK-INTERF
; Test whether failure due to cutoff for interference is reported
; RUN: llc -regalloc=greedy -relocation-model=pic -lcr-max-interf=1 -lcr-max-depth=0 -exhaustive-register-search < %s > %t 2>&1