https://github.com/spavloff created
https://github.com/llvm/llvm-project/pull/90877
Conversion of floating-point literal to binary representation must be made
using constant rounding mode, which can be changed using pragma FENV_ROUND. For
example, the literal "0.1F" should be representes by either 0.099999994 or
0.100000001 depending on the rounding direction.
>From 5d906b537636ca0d8706a8a888dd78edfbec684f Mon Sep 17 00:00:00 2001
From: Serge Pavlov <sepavl...@gmail.com>
Date: Thu, 2 May 2024 22:28:05 +0700
Subject: [PATCH] [clang] Use constant rounding mode for floating literals
Conversion of floating-point literal to binary representation must be
made using constant rounding mode, which can be changed using pragma
FENV_ROUND. For example, the literal "0.1F" should be representes by
either 0.099999994 or 0.100000001 depending on the rounding direction.
---
clang/include/clang/Lex/LiteralSupport.h | 10 ++++------
clang/lib/Lex/LiteralSupport.cpp | 6 +++---
clang/lib/Sema/SemaExpr.cpp | 3 ++-
clang/test/AST/const-fpfeatures.c | 6 ++++++
4 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/clang/include/clang/Lex/LiteralSupport.h
b/clang/include/clang/Lex/LiteralSupport.h
index 2ed42d1c5f9aae..705021fcfa5b11 100644
--- a/clang/include/clang/Lex/LiteralSupport.h
+++ b/clang/include/clang/Lex/LiteralSupport.h
@@ -118,12 +118,10 @@ class NumericLiteralParser {
/// bits of the result and return true. Otherwise, return false.
bool GetIntegerValue(llvm::APInt &Val);
- /// GetFloatValue - Convert this numeric literal to a floating value, using
- /// the specified APFloat fltSemantics (specifying float, double, etc).
- /// The optional bool isExact (passed-by-reference) has its value
- /// set to true if the returned APFloat can represent the number in the
- /// literal exactly, and false otherwise.
- llvm::APFloat::opStatus GetFloatValue(llvm::APFloat &Result);
+ /// Convert this numeric literal to a floating value, using the specified
+ /// APFloat fltSemantics (specifying float, double, etc) and rounding mode.
+ llvm::APFloat::opStatus GetFloatValue(llvm::APFloat &Result,
+ llvm::RoundingMode RM);
/// GetFixedPointValue - Convert this numeric literal value into a
/// scaled integer that represents this value. Returns true if an overflow
diff --git a/clang/lib/Lex/LiteralSupport.cpp b/clang/lib/Lex/LiteralSupport.cpp
index 9c0cbea5052cb2..3df0391bdda772 100644
--- a/clang/lib/Lex/LiteralSupport.cpp
+++ b/clang/lib/Lex/LiteralSupport.cpp
@@ -1520,7 +1520,8 @@ bool NumericLiteralParser::GetIntegerValue(llvm::APInt
&Val) {
}
llvm::APFloat::opStatus
-NumericLiteralParser::GetFloatValue(llvm::APFloat &Result) {
+NumericLiteralParser::GetFloatValue(llvm::APFloat &Result,
+ llvm::RoundingMode RM) {
using llvm::APFloat;
unsigned n = std::min(SuffixBegin - ThisTokBegin, ThisTokEnd - ThisTokBegin);
@@ -1534,8 +1535,7 @@ NumericLiteralParser::GetFloatValue(llvm::APFloat
&Result) {
Str = Buffer;
}
- auto StatusOrErr =
- Result.convertFromString(Str, APFloat::rmNearestTiesToEven);
+ auto StatusOrErr = Result.convertFromString(Str, RM);
assert(StatusOrErr && "Invalid floating point representation");
return !errorToBool(StatusOrErr.takeError()) ? *StatusOrErr
: APFloat::opInvalidOp;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 0cca02c338954a..db96c8692f2516 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -3858,7 +3858,8 @@ static Expr *BuildFloatingLiteral(Sema &S,
NumericLiteralParser &Literal,
using llvm::APFloat;
APFloat Val(Format);
- APFloat::opStatus result = Literal.GetFloatValue(Val);
+ APFloat::opStatus result =
+ Literal.GetFloatValue(Val, S.CurFPFeatures.getRoundingMode());
// Overflow is always an error, but underflow is only an error if
// we underflowed to zero (APFloat reports denormals as underflow).
diff --git a/clang/test/AST/const-fpfeatures.c
b/clang/test/AST/const-fpfeatures.c
index 6600ea27405d9c..247245c776fed1 100644
--- a/clang/test/AST/const-fpfeatures.c
+++ b/clang/test/AST/const-fpfeatures.c
@@ -19,6 +19,9 @@ float FI1u = 0xFFFFFFFFU;
float _Complex C1u = C0;
// CHECK: @C1u = {{.*}} { float, float } { float 0x3FF0000020000000, float
0x3FF0000020000000 }
+float FLu = 0.1F;
+// CHECK: @FLu = {{.*}} float 0x3FB9999980000000
+
#pragma STDC FENV_ROUND FE_DOWNWARD
@@ -35,3 +38,6 @@ float FI1d = 0xFFFFFFFFU;
float _Complex C1d = C0;
// CHECK: @C1d = {{.*}} { float, float } { float 1.000000e+00, float
1.000000e+00 }
+
+float FLd = 0.1F;
+// CHECK: @FLd = {{.*}} float 0x3FB99999A0000000
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