[llvm] r296677 - [APInt] Optimize APInt creation from uint64_t
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 1 13:06:18 PST 2017
Author: ctopper
Date: Wed Mar 1 15:06:18 2017
New Revision: 296677
URL: http://llvm.org/viewvc/llvm-project?rev=296677&view=rev
Log:
[APInt] Optimize APInt creation from uint64_t
Summary:
This patch moves the clearUnusedBits calls into the two different initialization paths for APInt from a uint64_t. This allows the compiler to better optimize the clearing of the unused bits for the single word case. And it puts the clearing for the multi word case into the initSlowCase function to save code. In the common case of initializing with 0 this allows the clearing to be completely optimized out for the single word case.
On my local x86 build this is showing a ~45kb reduction in the size of the opt binary.
Reviewers: RKSimon, hans, majnemer, davide, MatzeB
Reviewed By: hans
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D30486
Modified:
llvm/trunk/include/llvm/ADT/APInt.h
llvm/trunk/lib/Support/APInt.cpp
Modified: llvm/trunk/include/llvm/ADT/APInt.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/APInt.h?rev=296677&r1=296676&r2=296677&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/APInt.h (original)
+++ llvm/trunk/include/llvm/ADT/APInt.h Wed Mar 1 15:06:18 2017
@@ -240,11 +240,12 @@ public:
APInt(unsigned numBits, uint64_t val, bool isSigned = false)
: BitWidth(numBits), VAL(0) {
assert(BitWidth && "bitwidth too small");
- if (isSingleWord())
+ if (isSingleWord()) {
VAL = val;
- else
+ clearUnusedBits();
+ } else {
initSlowCase(val, isSigned);
- clearUnusedBits();
+ }
}
/// \brief Construct an APInt of numBits width, initialized as bigVal[].
Modified: llvm/trunk/lib/Support/APInt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APInt.cpp?rev=296677&r1=296676&r2=296677&view=diff
==============================================================================
--- llvm/trunk/lib/Support/APInt.cpp (original)
+++ llvm/trunk/lib/Support/APInt.cpp Wed Mar 1 15:06:18 2017
@@ -81,6 +81,7 @@ void APInt::initSlowCase(uint64_t val, b
if (isSigned && int64_t(val) < 0)
for (unsigned i = 1; i < getNumWords(); ++i)
pVal[i] = -1ULL;
+ clearUnusedBits();
}
void APInt::initSlowCase(const APInt& that) {
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