[llvm-commits] [llvm] r123206 - in /llvm/trunk: lib/Analysis/ConstantFolding.cpp lib/Target/README.txt test/Transforms/ConstProp/calls.ll
Chandler Carruth
chandlerc at gmail.com
Mon Jan 10 17:07:24 PST 2011
Author: chandlerc
Date: Mon Jan 10 19:07:24 2011
New Revision: 123206
URL: http://llvm.org/viewvc/llvm-project?rev=123206&view=rev
Log:
Teach constant folding to perform conversions from constant floating
point values to their integer representation through the SSE intrinsic
calls. This is the last part of a README.txt entry for which I have real
world examples.
Modified:
llvm/trunk/lib/Analysis/ConstantFolding.cpp
llvm/trunk/lib/Target/README.txt
llvm/trunk/test/Transforms/ConstProp/calls.ll
Modified: llvm/trunk/lib/Analysis/ConstantFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ConstantFolding.cpp?rev=123206&r1=123205&r2=123206&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp (original)
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp Mon Jan 10 19:07:24 2011
@@ -1047,6 +1047,14 @@
case Intrinsic::smul_with_overflow:
case Intrinsic::convert_from_fp16:
case Intrinsic::convert_to_fp16:
+ case Intrinsic::x86_sse_cvtss2si:
+ case Intrinsic::x86_sse_cvtss2si64:
+ case Intrinsic::x86_sse_cvttss2si:
+ case Intrinsic::x86_sse_cvttss2si64:
+ case Intrinsic::x86_sse2_cvtsd2si:
+ case Intrinsic::x86_sse2_cvtsd2si64:
+ case Intrinsic::x86_sse2_cvttsd2si:
+ case Intrinsic::x86_sse2_cvttsd2si64:
return true;
default:
return false;
@@ -1116,6 +1124,36 @@
return 0; // dummy return to suppress warning
}
+/// ConstantFoldConvertToInt - Attempt to an SSE floating point to integer
+/// conversion of a constant floating point. If roundTowardZero is false, the
+/// default IEEE rounding is used (toward nearest, ties to even). This matches
+/// the behavior of the non-truncating SSE instructions in the default rounding
+/// mode. The desired integer type Ty is used to select how many bits are
+/// available for the result. Returns null if the conversion cannot be
+/// performed, otherwise returns the Constant value resulting from the
+/// conversion.
+static Constant *ConstantFoldConvertToInt(ConstantFP *Op, bool roundTowardZero,
+ const Type *Ty) {
+ assert(Op && "Called with NULL operand");
+ APFloat Val(Op->getValueAPF());
+
+ // All of these conversion intrinsics form an integer of at most 64bits.
+ unsigned ResultWidth = cast<IntegerType>(Ty)->getBitWidth();
+ assert(ResultWidth <= 64 &&
+ "Can only constant fold conversions to 64 and 32 bit ints");
+
+ uint64_t UIntVal;
+ bool isExact = false;
+ APFloat::roundingMode mode = roundTowardZero? APFloat::rmTowardZero
+ : APFloat::rmNearestTiesToEven;
+ APFloat::opStatus status = Val.convertToInteger(&UIntVal, ResultWidth,
+ /*isSigned=*/true, mode,
+ &isExact);
+ if (status != APFloat::opOK && status != APFloat::opInexact)
+ return 0;
+ return ConstantInt::get(Ty, UIntVal, /*isSigned=*/true);
+}
+
/// ConstantFoldCall - Attempt to constant fold a call to the specified function
/// with the specified arguments, returning null if unsuccessful.
Constant *
@@ -1246,6 +1284,24 @@
}
}
+ if (ConstantVector *Op = dyn_cast<ConstantVector>(Operands[0])) {
+ switch (F->getIntrinsicID()) {
+ default: break;
+ case Intrinsic::x86_sse_cvtss2si:
+ case Intrinsic::x86_sse_cvtss2si64:
+ case Intrinsic::x86_sse2_cvtsd2si:
+ case Intrinsic::x86_sse2_cvtsd2si64:
+ if (ConstantFP *FPOp = dyn_cast<ConstantFP>(Op->getOperand(0)))
+ return ConstantFoldConvertToInt(FPOp, /*roundTowardZero=*/false, Ty);
+ case Intrinsic::x86_sse_cvttss2si:
+ case Intrinsic::x86_sse_cvttss2si64:
+ case Intrinsic::x86_sse2_cvttsd2si:
+ case Intrinsic::x86_sse2_cvttsd2si64:
+ if (ConstantFP *FPOp = dyn_cast<ConstantFP>(Op->getOperand(0)))
+ return ConstantFoldConvertToInt(FPOp, /*roundTowardZero=*/true, Ty);
+ }
+ }
+
if (isa<UndefValue>(Operands[0])) {
if (F->getIntrinsicID() == Intrinsic::bswap)
return Operands[0];
Modified: llvm/trunk/lib/Target/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/README.txt?rev=123206&r1=123205&r2=123206&view=diff
==============================================================================
--- llvm/trunk/lib/Target/README.txt (original)
+++ llvm/trunk/lib/Target/README.txt Mon Jan 10 19:07:24 2011
@@ -2259,58 +2259,3 @@
transform the fmul to 0.0, and then the fadd to 2.0.
//===---------------------------------------------------------------------===//
-
-clang -O3 currently compiles this code:
-
-#include <emmintrin.h>
-int f(double x) { return _mm_cvtsd_si32(_mm_set_sd(x)); }
-int g(double x) { return _mm_cvttsd_si32(_mm_set_sd(x)); }
-
-into
-
-define i32 @_Z1fd(double %x) nounwind readnone {
-entry:
- %vecinit.i = insertelement <2 x double> undef, double %x, i32 0
- %vecinit1.i = insertelement <2 x double> %vecinit.i, double 0.000000e+00,i32 1
- %0 = tail call i32 @llvm.x86.sse2.cvtsd2si(<2 x double> %vecinit1.i) nounwind
- ret i32 %0
-}
-
-define i32 @_Z1gd(double %x) nounwind readnone {
-entry:
- %conv.i = fptosi double %x to i32
- ret i32 %conv.i
-}
-
-This difference carries over to the assmebly produced, resulting in:
-
-_Z1fd: # @_Z1fd
-# BB#0: # %entry
- pushq %rbp
- movq %rsp, %rbp
- xorps %xmm1, %xmm1
- movsd %xmm0, %xmm1
- cvtsd2sil %xmm1, %eax
- popq %rbp
- ret
-
-_Z1gd: # @_Z1gd
-# BB#0: # %entry
- pushq %rbp
- movq %rsp, %rbp
- cvttsd2si %xmm0, %eax
- popq %rbp
- ret
-
-The problem is that we can't see through the intrinsic call used for cvtsd2si,
-and fold away the unnecessary manipulation of the function parameter. When
-these functions are inlined, it forms a barrier preventing many further
-optimizations. LLVM IR doesn't have a good way to model the logic of
-'cvtsd2si', its only FP -> int conversion path forces truncation. We should add
-a rounding flag onto fptosi so that it can represent this type of rounding
-naturally in the IR rather than using intrinsics. We might need to use a
-'system_rounding_mode' flag to encode that the semantics of the rounding mode
-can be changed by the program, but ideally we could just say that isn't
-supported, and hard code the rounding.
-
-//===---------------------------------------------------------------------===//
Modified: llvm/trunk/test/Transforms/ConstProp/calls.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/ConstProp/calls.ll?rev=123206&r1=123205&r2=123206&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/ConstProp/calls.ll (original)
+++ llvm/trunk/test/Transforms/ConstProp/calls.ll Mon Jan 10 19:07:24 2011
@@ -21,3 +21,36 @@
%c = fadd double %b, %D
ret double %c
}
+
+define i1 @test_sse_cvt() nounwind readnone {
+; CHECK: @test_sse_cvt
+; CHECK-NOT: call
+; CHECK: ret i1 true
+entry:
+ %i0 = tail call i32 @llvm.x86.sse.cvtss2si(<4 x float> <float 1.75, float undef, float undef, float undef>) nounwind
+ %i1 = tail call i32 @llvm.x86.sse.cvttss2si(<4 x float> <float 1.75, float undef, float undef, float undef>) nounwind
+ %i2 = tail call i64 @llvm.x86.sse.cvtss2si64(<4 x float> <float 1.75, float undef, float undef, float undef>) nounwind
+ %i3 = tail call i64 @llvm.x86.sse.cvttss2si64(<4 x float> <float 1.75, float undef, float undef, float undef>) nounwind
+ %i4 = call i32 @llvm.x86.sse2.cvtsd2si(<2 x double> <double 1.75, double undef>) nounwind
+ %i5 = call i32 @llvm.x86.sse2.cvttsd2si(<2 x double> <double 1.75, double undef>) nounwind
+ %i6 = call i64 @llvm.x86.sse2.cvtsd2si64(<2 x double> <double 1.75, double undef>) nounwind
+ %i7 = call i64 @llvm.x86.sse2.cvttsd2si64(<2 x double> <double 1.75, double undef>) nounwind
+ %sum11 = add i32 %i0, %i1
+ %sum12 = add i32 %i4, %i5
+ %sum1 = add i32 %sum11, %sum12
+ %sum21 = add i64 %i2, %i3
+ %sum22 = add i64 %i6, %i7
+ %sum2 = add i64 %sum21, %sum22
+ %sum1.sext = sext i32 %sum1 to i64
+ %b = icmp eq i64 %sum1.sext, %sum2
+ ret i1 %b
+}
+
+declare i32 @llvm.x86.sse.cvtss2si(<4 x float>) nounwind readnone
+declare i32 @llvm.x86.sse.cvttss2si(<4 x float>) nounwind readnone
+declare i64 @llvm.x86.sse.cvtss2si64(<4 x float>) nounwind readnone
+declare i64 @llvm.x86.sse.cvttss2si64(<4 x float>) nounwind readnone
+declare i32 @llvm.x86.sse2.cvtsd2si(<2 x double>) nounwind readnone
+declare i32 @llvm.x86.sse2.cvttsd2si(<2 x double>) nounwind readnone
+declare i64 @llvm.x86.sse2.cvtsd2si64(<2 x double>) nounwind readnone
+declare i64 @llvm.x86.sse2.cvttsd2si64(<2 x double>) nounwind readnone
More information about the llvm-commits
mailing list