[llvm] r234898 - The code that originally made me discover this is:
Daniel Jasper
djasper at google.com
Tue Apr 14 16:38:39 PDT 2015
What made you think it was this change that broke it? The test passed fine
locally and still does if I re-apply the patch.
On Tue, Apr 14, 2015 at 6:00 PM, Rafael Espíndola <
rafael.espindola at gmail.com> wrote:
> reverted because CodeGen/ARM/2013-10-11-select-stalls.ll was failing.
>
> On 14 April 2015 at 16:20, Daniel Jasper <djasper at google.com> wrote:
> > Author: djasper
> > Date: Tue Apr 14 10:20:37 2015
> > New Revision: 234898
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=234898&view=rev
> > Log:
> > The code that originally made me discover this is:
> >
> > if ((a & 0x1) == 0x1) {
> > ..
> > }
> >
> > In this case we don't actually have any branch probability information
> and
> > should not assume to have any. LLVM transforms this into:
> >
> > %and = and i32 %a, 1
> > %tobool = icmp eq i32 %and, 0
> >
> > So, in this case, the result of a bitwise and is compared against 0,
> > but nevertheless, we should not assume to have probability
> > information.
> >
> > Modified:
> > llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp
> > llvm/trunk/test/Analysis/BranchProbabilityInfo/basic.ll
> > llvm/trunk/test/CodeGen/AArch64/arm64-call-tailcalls.ll
> > llvm/trunk/test/CodeGen/Mips/octeon.ll
> >
> > Modified: llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp?rev=234898&r1=234897&r2=234898&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp (original)
> > +++ llvm/trunk/lib/Analysis/BranchProbabilityInfo.cpp Tue Apr 14
> 10:20:37 2015
> > @@ -379,6 +379,14 @@ bool BranchProbabilityInfo::calcZeroHeur
> > if (!CV)
> > return false;
> >
> > + // If the LHS is the result of AND'ing a value with a single bit
> bitmask,
> > + // we don't have information about probabilities.
> > + if (Instruction *LHS = dyn_cast<Instruction>(CI->getOperand(0)))
> > + if (LHS->getOpcode() == Instruction::And)
> > + if (ConstantInt *AndRHS =
> dyn_cast<ConstantInt>(LHS->getOperand(1)))
> > + if (AndRHS->getUniqueInteger().isPowerOf2())
> > + return false;
> > +
> > bool isProb;
> > if (CV->isZero()) {
> > switch (CI->getPredicate()) {
> >
> > Modified: llvm/trunk/test/Analysis/BranchProbabilityInfo/basic.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BranchProbabilityInfo/basic.ll?rev=234898&r1=234897&r2=234898&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/test/Analysis/BranchProbabilityInfo/basic.ll (original)
> > +++ llvm/trunk/test/Analysis/BranchProbabilityInfo/basic.ll Tue Apr 14
> 10:20:37 2015
> > @@ -212,3 +212,31 @@ exit:
> > ret i32 %result
> > }
> >
> > +define i32 @zero3(i32 %i, i32 %a, i32 %b) {
> > +; CHECK: Printing analysis {{.*}} for function 'zero3'
> > +entry:
> > +; AND'ing with a single bit bitmask essentially leads to a bool
> comparison,
> > +; meaning we don't have probability information.
> > + %and = and i32 %i, 2
> > + %tobool = icmp eq i32 %and, 0
> > + br i1 %tobool, label %then, label %else
> > +; CHECK: edge entry -> then probability is 16 / 32
> > +; CHECK: edge entry -> else probability is 16 / 32
> > +
> > +then:
> > +; AND'ing with other bitmask might be something else, so we still
> assume the
> > +; usual probabilities.
> > + %and2 = and i32 %i, 5
> > + %tobool2 = icmp eq i32 %and2, 0
> > + br i1 %tobool2, label %else, label %exit
> > +; CHECK: edge then -> else probability is 12 / 32
> > +; CHECK: edge then -> exit probability is 20 / 32
> > +
> > +else:
> > + br label %exit
> > +
> > +exit:
> > + %result = phi i32 [ %a, %then ], [ %b, %else ]
> > + ret i32 %result
> > +}
> > +
> >
> > Modified: llvm/trunk/test/CodeGen/AArch64/arm64-call-tailcalls.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/arm64-call-tailcalls.ll?rev=234898&r1=234897&r2=234898&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/test/CodeGen/AArch64/arm64-call-tailcalls.ll (original)
> > +++ llvm/trunk/test/CodeGen/AArch64/arm64-call-tailcalls.ll Tue Apr 14
> 10:20:37 2015
> > @@ -53,9 +53,9 @@ bb:
> >
> > define i32 @t8(i32 %x) nounwind ssp {
> > ; CHECK-LABEL: t8:
> > +; CHECK: b _c
> > ; CHECK: b _a
> > ; CHECK: b _b
> > -; CHECK: b _c
> > %and = and i32 %x, 1
> > %tobool = icmp eq i32 %and, 0
> > br i1 %tobool, label %if.end, label %if.then
> >
> > Modified: llvm/trunk/test/CodeGen/Mips/octeon.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Mips/octeon.ll?rev=234898&r1=234897&r2=234898&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/test/CodeGen/Mips/octeon.ll (original)
> > +++ llvm/trunk/test/CodeGen/Mips/octeon.ll Tue Apr 14 10:20:37 2015
> > @@ -93,7 +93,7 @@ entry:
> > ; ALL-LABEL: bbit0:
> > ; OCTEON: bbit0 $4, 3, $[[BB0:BB[0-9_]+]]
> > ; MIPS64: andi $[[T0:[0-9]+]], $4, 8
> > -; MIPS64: beqz $[[T0]], $[[BB0:BB[0-9_]+]]
> > +; MIPS64: bnez $[[T0]], $[[BB0:BB[0-9_]+]]
> > %bit = and i64 %a, 8
> > %res = icmp eq i64 %bit, 0
> > br i1 %res, label %endif, label %if
> > @@ -111,7 +111,7 @@ entry:
> > ; MIPS64: daddiu $[[T0:[0-9]+]], $zero, 1
> > ; MIPS64: dsll $[[T1:[0-9]+]], $[[T0]], 35
> > ; MIPS64: and $[[T2:[0-9]+]], $4, $[[T1]]
> > -; MIPS64: beqz $[[T2]], $[[BB0:BB[0-9_]+]]
> > +; MIPS64: bnez $[[T2]], $[[BB0:BB[0-9_]+]]
> > %bit = and i64 %a, 34359738368
> > %res = icmp eq i64 %bit, 0
> > br i1 %res, label %endif, label %if
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
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