This rewrites big parts of the fast register allocator. The basic
strategy of doing block-local allocation hasn't changed but I tweaked
several details:
Track register state on register units instead of physical
registers. This simplifies and speeds up handling of register aliases.
Process basic blocks in reverse order: Definitions are known to end
register livetimes when walking backwards (contrary when walking
forward then uses may or may not be a kill so we need heuristics).
Check register mask operands (calls) instead of conservatively
assuming everything is clobbered. Enhance heuristics to detect
killing uses: In case of a small number of defs/uses check if they are
all in the same basic block and if so the last one is a killing use.
Enhance heuristic for copy-coalescing through hinting: We check the
first k defs of a register for COPYs rather than relying on there just
being a single definition. When testing this on the full llvm
test-suite including SPEC externals I measured:
average 5.1% reduction in code size for X86, 4.9% reduction in code on
aarch64. (ranging between 0% and 20% depending on the test) 0.5%
faster compiletime (some analysis suggests the pass is slightly slower
than before, but we more than make up for it because later passes are
faster with the reduced instruction count)
Also adds a few testcases that were broken without this patch, in
particular bug 47278.
Patch mostly by Matthias Braun
VSX provides a full complement of rounding instructions yet we somehow ended up
with some of them legal and others not. This just legalizes all of the FP
rounding nodes and the FP -> int rounding nodes with unsafe math.
Differential revision: https://reviews.llvm.org/D69949
Summary:
This is brought up in
https://reviews.llvm.org/D64662?id=209923#inline-599490
CFI information are non-relevant to quite some testcases,
we should get rid of checking them when its unecessary.
This patch avoid generating cfi info in testcases that are not
testing prolog/epilog or exception handling.
Reviewers: kbarton, hfinkel, nemanjai, #powerpc
Reviewed By: hfinkel
Subscribers: MaskRay, shchenz, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67016
llvm-svn: 370505
The 2nd loop calculates spill costs but reports free registers as cost
0 anyway, so there is little benefit from having a separate early
loop.
Surprisingly this is not NFC, as many register are marked regDisabled
so the first loop often picks up later registers unnecessarily instead
of the first one available in the allocation order...
Patch by Matthias Braun
llvm-svn: 356499
As noted in the D44909 review, the transform from (fptosi+sitofp) to ftrunc
can produce -0.0 where the original code does not:
#include <stdio.h>
int main(int argc) {
float x;
x = -0.8 * argc;
printf("%f\n", (float)((int)x));
return 0;
}
$ clang -O0 -mavx fp.c ; ./a.out
0.000000
$ clang -O1 -mavx fp.c ; ./a.out
-0.000000
Ideally, we'd use IR/node flags to predicate the transform, but the IR parser
doesn't currently allow fast-math-flags on the cast instructions. So for now,
just use the function attribute that corresponds to clang's "-fno-signed-zeros"
option.
Differential Revision: https://reviews.llvm.org/D48085
llvm-svn: 335761
This was originally committed at rL328921 and reverted at rL329920 to
investigate failures in Chrome. This time I've added to the ReleaseNotes
to warn users of the potential of exposing UB and let me repeat that
here for more exposure:
Optimization of floating-point casts is improved. This may cause surprising
results for code that is relying on undefined behavior. Code sanitizers can
be used to detect affected patterns such as this:
int main() {
float x = 4294967296.0f;
x = (float)((int)x);
printf("junk in the ftrunc: %f\n", x);
return 0;
}
$ clang -O1 ftrunc.c -fsanitize=undefined ; ./a.out
ftrunc.c:5:15: runtime error: 4.29497e+09 is outside the range of
representable values of type 'int'
junk in the ftrunc: 0.000000
Original commit message:
fptosi / fptoui round towards zero, and that's the same behavior as ISD::FTRUNC,
so replace a pair of casts with the equivalent node. We don't have to account for
special cases (NaN, INF) because out-of-range casts are undefined.
Differential Revision: https://reviews.llvm.org/D44909
llvm-svn: 330437
This change is exposing UB in source code - as was warned/predicted. :)
See D44909 for discussion. Reverting while we figure out how to fix things.
llvm-svn: 329920
fptosi / fptoui round towards zero, and that's the same behavior as ISD::FTRUNC,
so replace a pair of casts with the equivalent node. We don't have to account for
special cases (NaN, INF) because out-of-range casts are undefined.
Differential Revision: https://reviews.llvm.org/D44909
llvm-svn: 328921
Summary:
Fix an issue that's similar to what D41411 fixed:
float(__int128(float_var)) shouldn't be optimized to xscvdpsxds +
xscvsxdsp, as they mean (float)(int64_t)float_var.
Reviewers: jtony, hfinkel, echristo
Subscribers: sanjoy, nemanjai, hiraditya, llvm-commits, kbarton
Differential Revision: https://reviews.llvm.org/D42400
llvm-svn: 323270
serge-sans-paille