Commit Graph

6 Commits

Author SHA1 Message Date
David Majnemer 8b16da8744 [InstCombine] Do not RAUW a constant GEP
canRewriteGEPAsOffset expects to process instructions, not constants.

This fixes PR30342.

llvm-svn: 281650
2016-09-15 20:10:09 +00:00
Silviu Baranga f29dfd36bb Re-commit r257064, after it was reverted in r257340.
This contains a fix for the issue that caused the revert:
we no longer assume that we can insert instructions after the
instruction that produces the base pointer. We previously
assumed that this would be ok, because the instruction produces
a value and therefore is not a terminator. This is false for invoke
instructions. We will now insert these new instruction directly
at the location of the users.

Original commit message:

[InstCombine] Look through PHIs, GEPs, IntToPtrs and PtrToInts to expose more constants when comparing GEPs

Summary:
When comparing two GEP instructions which have the same base pointer
and one of them has a constant index, it is possible to only compare
indices, transforming it to a compare with a constant. This removes
one use for the GEP instruction with the constant index, can reduce
register pressure and can sometimes lead to removing the comparisson
entirely.

InstCombine was already doing this when comparing two GEPs if the base
pointers were the same. However, in the case where we have complex
pointer arithmetic (GEPs applied to GEPs, PHIs of GEPs, conversions to
or from integers, etc) the value of the original base pointer will be
hidden to the optimizer and this transformation will be disabled.

This change detects when the two sides of the comparison can be
expressed as GEPs with the same base pointer, even if they don't
appear as such in the IR. The transformation will convert all the
pointer arithmetic to arithmetic done on indices and all the relevant
uses of GEPs to GEPs with a common base pointer. The GEP comparison
will be converted to a comparison done on indices.

Reviewers: majnemer, jmolloy

Subscribers: hfinkel, jevinskie, jmolloy, aadg, llvm-commits

Differential Revision: http://reviews.llvm.org/D15146

llvm-svn: 257897
2016-01-15 15:52:05 +00:00
Silviu Baranga 603954ef0e Revert r257164 - it has caused spec2k6 failures in LTO mode
llvm-svn: 257340
2016-01-11 16:19:38 +00:00
Silviu Baranga 9e007efad2 Re-commit r257064, this time with a fixed assert
In setInsertionPoint if the value is not a PHI, Instruction or
Argument it should be a Constant, not a ConstantExpr.

Original commit message:

[InstCombine] Look through PHIs, GEPs, IntToPtrs and PtrToInts to expose more constants when comparing GEPs

Summary:
When comparing two GEP instructions which have the same base pointer
and one of them has a constant index, it is possible to only compare
indices, transforming it to a compare with a constant. This removes
one use for the GEP instruction with the constant index, can reduce
register pressure and can sometimes lead to removing the comparisson
entirely.

InstCombine was already doing this when comparing two GEPs if the base
pointers were the same. However, in the case where we have complex
pointer arithmetic (GEPs applied to GEPs, PHIs of GEPs, conversions to
or from integers, etc) the value of the original base pointer will be
hidden to the optimizer and this transformation will be disabled.

This change detects when the two sides of the comparison can be
expressed as GEPs with the same base pointer, even if they don't
appear as such in the IR. The transformation will convert all the
pointer arithmetic to arithmetic done on indices and all the relevant
uses of GEPs to GEPs with a common base pointer. The GEP comparison
will be converted to a comparison done on indices.

Reviewers: majnemer, jmolloy

Subscribers: hfinkel, jevinskie, jmolloy, aadg, llvm-commits

Differential Revision: http://reviews.llvm.org/D15146

llvm-svn: 257164
2016-01-08 11:11:04 +00:00
Silviu Baranga dd68d46ec1 Revert r257064. It caused failures in some sanitizer tests.
llvm-svn: 257069
2016-01-07 15:46:43 +00:00
Silviu Baranga 57b1b90996 [InstCombine] Look through PHIs, GEPs, IntToPtrs and PtrToInts to expose more constants when comparing GEPs
Summary:
When comparing two GEP instructions which have the same base pointer
and one of them has a constant index, it is possible to only compare
indices, transforming it to a compare with a constant. This removes
one use for the GEP instruction with the constant index, can reduce
register pressure and can sometimes lead to removing the comparisson
entirely.

InstCombine was already doing this when comparing two GEPs if the
base pointers were the same. However, in the case where we have
complex pointer arithmetic (GEPs applied to GEPs, PHIs of GEPs,
conversions to or from integers, etc) the value of the original
base pointer will be hidden to the optimizer and this transformation
will be disabled.

This change detects when the two sides of the comparison can be
expressed as GEPs with the same base pointer, even if they don't
appear as such in the IR. The transformation will convert all the
pointer arithmetic to arithmetic done on indices and all the
relevant uses of GEPs to GEPs with a common base pointer. The
GEP comparison will be converted to a comparison done on indices.

Reviewers: majnemer, jmolloy

Subscribers: hfinkel, jevinskie, jmolloy, aadg, llvm-commits

Differential Revision: http://reviews.llvm.org/D15146

llvm-svn: 257064
2016-01-07 14:56:08 +00:00