Bypass Slow Divides
* Only apply divide bypass optimization when not optimizing for size.
* Fixed bug caused by constant for 0 value of type Int32,
used dividend type to generate the constant instead.
* For atom x86-64 apply the divide bypass to use 16-bit divides instead of
64-bit divides when operand values are small enough.
* Added lit tests for 64-bit divide bypass.
Patch by Tyler Nowicki!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176442 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 451acca..5d12b0a 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -181,9 +181,12 @@
setSchedulingPreference(Sched::RegPressure);
setStackPointerRegisterToSaveRestore(RegInfo->getStackRegister());
- // Bypass i32 with i8 on Atom when compiling with O2
- if (Subtarget->hasSlowDivide() && TM.getOptLevel() >= CodeGenOpt::Default)
+ // Bypass expensive divides on Atom when compiling with O2
+ if (Subtarget->hasSlowDivide() && TM.getOptLevel() >= CodeGenOpt::Default) {
addBypassSlowDiv(32, 8);
+ if (Subtarget->is64Bit())
+ addBypassSlowDiv(64, 16);
+ }
if (Subtarget->isTargetWindows() && !Subtarget->isTargetCygMing()) {
// Setup Windows compiler runtime calls.
diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index d71dd5d..015fd2e 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -154,7 +154,7 @@
/// This optimization identifies DIV instructions that can be
/// profitably bypassed and carried out with a shorter, faster divide.
- if (TLI && TLI->isSlowDivBypassed()) {
+ if (!OptSize && TLI && TLI->isSlowDivBypassed()) {
const DenseMap<unsigned int, unsigned int> &BypassWidths =
TLI->getBypassSlowDivWidths();
for (Function::iterator I = F.begin(); I != F.end(); I++)
diff --git a/lib/Transforms/Utils/BypassSlowDivision.cpp b/lib/Transforms/Utils/BypassSlowDivision.cpp
index 00cda8e..1f517d0 100644
--- a/lib/Transforms/Utils/BypassSlowDivision.cpp
+++ b/lib/Transforms/Utils/BypassSlowDivision.cpp
@@ -163,7 +163,7 @@
Value *AndV = MainBuilder.CreateAnd(OrV, BitMask);
// Compare operand values and branch
- Value *ZeroV = MainBuilder.getInt32(0);
+ Value *ZeroV = ConstantInt::getSigned(Dividend->getType(), 0);
Value *CmpV = MainBuilder.CreateICmpEQ(AndV, ZeroV);
MainBuilder.CreateCondBr(CmpV, FastBB, SlowBB);
@@ -244,7 +244,7 @@
// Get bitwidth of div/rem instruction
IntegerType *T = cast<IntegerType>(J->getType());
- int bitwidth = T->getBitWidth();
+ unsigned int bitwidth = T->getBitWidth();
// Continue if bitwidth is not bypassed
DenseMap<unsigned int, unsigned int>::const_iterator BI = BypassWidths.find(bitwidth);
diff --git a/test/CodeGen/X86/atom-bypass-slow-division-64.ll b/test/CodeGen/X86/atom-bypass-slow-division-64.ll
new file mode 100644
index 0000000..a3bbea3
--- /dev/null
+++ b/test/CodeGen/X86/atom-bypass-slow-division-64.ll
@@ -0,0 +1,46 @@
+; RUN: llc < %s -mcpu=atom -mtriple=i686-linux -march=x86-64 | FileCheck %s
+
+; Additional tests for 64-bit divide bypass
+
+define i64 @Test_get_quotient(i64 %a, i64 %b) nounwind {
+; CHECK: Test_get_quotient:
+; CHECK: orq %rsi, %rcx
+; CHECK-NEXT: testq $-65536, %rcx
+; CHECK-NEXT: je
+; CHECK: idivq
+; CHECK: ret
+; CHECK: divw
+; CHECK: ret
+ %result = sdiv i64 %a, %b
+ ret i64 %result
+}
+
+define i64 @Test_get_remainder(i64 %a, i64 %b) nounwind {
+; CHECK: Test_get_remainder:
+; CHECK: orq %rsi, %rcx
+; CHECK-NEXT: testq $-65536, %rcx
+; CHECK-NEXT: je
+; CHECK: idivq
+; CHECK: ret
+; CHECK: divw
+; CHECK: ret
+ %result = srem i64 %a, %b
+ ret i64 %result
+}
+
+define i64 @Test_get_quotient_and_remainder(i64 %a, i64 %b) nounwind {
+; CHECK: Test_get_quotient_and_remainder:
+; CHECK: orq %rsi, %rcx
+; CHECK-NEXT: testq $-65536, %rcx
+; CHECK-NEXT: je
+; CHECK: idivq
+; CHECK: divw
+; CHECK: addq
+; CHECK: ret
+; CHECK-NOT: idivq
+; CHECK-NOT: divw
+ %resultdiv = sdiv i64 %a, %b
+ %resultrem = srem i64 %a, %b
+ %result = add i64 %resultdiv, %resultrem
+ ret i64 %result
+}
diff --git a/test/CodeGen/X86/atom-bypass-slow-division.ll b/test/CodeGen/X86/atom-bypass-slow-division.ll
index 453e726..4612940 100644
--- a/test/CodeGen/X86/atom-bypass-slow-division.ll
+++ b/test/CodeGen/X86/atom-bypass-slow-division.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -mcpu=atom -mtriple=i686-linux | FileCheck %s
+; RUN: llc < %s -mcpu=atom -mtriple=i686-linux | FileCheck %s
define i32 @Test_get_quotient(i32 %a, i32 %b) nounwind {
; CHECK: Test_get_quotient: