llvm-project

Commit Graph

Author	SHA1	Message	Date
Benjamin Kramer	5b455f0b62	[SDAG] Now that we have a way to communicate the exact bit on sdiv use it to simplify sdiv by a constant. We had a hack in SDAGBuilder in place to work around this but now we can avoid that. Call BuildExactSDIV from BuildSDIV so DAGCombiner can perform this trick automatically. The added check in DAGCombiner is necessary to prevent exact sdiv by pow2 from regressing as the target-specific pow2 lowering is not aware of exact bits yet. This is mostly covered by existing tests. One side effect is that we get the better lowering for exact vector sdivs now too :) llvm-svn: 240891	2015-06-27 20:33:26 +00:00
Stephen Lin	f799e3f944	Convert CodeGen//.ll tests to use the new CHECK-LABEL for easier debugging. No functionality change and all tests pass after conversion. This was done with the following sed invocation to catch label lines demarking function boundaries: sed -i '' "s/^;\( \)\([A-Z0-9_]\):\( \)test\([A-Za-z0-9_-]\):\( \)$/;\1\2-LABEL:\3test\4:\5/g" test/CodeGen//*.ll which was written conservatively to avoid false positives rather than false negatives. I scanned through all the changes and everything looks correct. llvm-svn: 186258	2013-07-13 20:38:47 +00:00
Benjamin Kramer	9960a25006	Emit a more efficient magic number multiplication for exact sdivs. We have to do this in DAGBuilder instead of DAGCombiner, because the exact bit is lost after building. struct foo { char x[24]; }; long bar(struct foo a, struct foo b) { return a-b; } is now compiled into movl 4(%esp), %eax subl 8(%esp), %eax sarl $3, %eax imull $-1431655765, %eax, %eax instead of movl 4(%esp), %eax subl 8(%esp), %eax movl $715827883, %ecx imull %ecx movl %edx, %eax shrl $31, %eax sarl $2, %edx addl %eax, %edx movl %edx, %eax llvm-svn: 134695	2011-07-08 10:31:30 +00:00

Author

SHA1

Message

Date

Benjamin Kramer

5b455f0b62

[SDAG] Now that we have a way to communicate the exact bit on sdiv use it to simplify sdiv by a constant.

We had a hack in SDAGBuilder in place to work around this but now we
can avoid that. Call BuildExactSDIV from BuildSDIV so DAGCombiner can
perform this trick automatically.

The added check in DAGCombiner is necessary to prevent exact sdiv by pow2
from regressing as the target-specific pow2 lowering is not aware of
exact bits yet.

This is mostly covered by existing tests. One side effect is that we
get the better lowering for exact vector sdivs now too :)

llvm-svn: 240891

2015-06-27 20:33:26 +00:00

Stephen Lin

f799e3f944

Convert CodeGen/*/*.ll tests to use the new CHECK-LABEL for easier debugging. No functionality change and all tests pass after conversion.

This was done with the following sed invocation to catch label lines demarking function boundaries:
    sed -i '' "s/^;\( *\)\([A-Z0-9_]*\):\( *\)test\([A-Za-z0-9_-]*\):\( *\)$/;\1\2-LABEL:\3test\4:\5/g" test/CodeGen/*/*.ll
which was written conservatively to avoid false positives rather than false negatives. I scanned through all the changes and everything looks correct.

llvm-svn: 186258

2013-07-13 20:38:47 +00:00

Benjamin Kramer

9960a25006

Emit a more efficient magic number multiplication for exact sdivs.

We have to do this in DAGBuilder instead of DAGCombiner, because the exact bit is lost after building.

  struct foo { char x[24]; };
  long bar(struct foo *a, struct foo *b) { return a-b; }
is now compiled into
  movl	4(%esp), %eax
  subl	8(%esp), %eax
  sarl	$3, %eax
  imull	$-1431655765, %eax, %eax
instead of
  movl	4(%esp), %eax
  subl	8(%esp), %eax
  movl	$715827883, %ecx
  imull	%ecx
  movl	%edx, %eax
  shrl	$31, %eax
  sarl	$2, %edx
  addl	%eax, %edx
  movl	%edx, %eax

llvm-svn: 134695

2011-07-08 10:31:30 +00:00

3 Commits