[clang] e620035 - [clang] Use current rounding mode for float inc/dec (#73770)
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Thu Nov 30 02:33:40 PST 2023
Author: Serge Pavlov
Date: 2023-11-30T17:33:35+07:00
New Revision: e620035a28d5d957623aa7b4aeda35ab5130e2c9
URL: https://github.com/llvm/llvm-project/commit/e620035a28d5d957623aa7b4aeda35ab5130e2c9
DIFF: https://github.com/llvm/llvm-project/commit/e620035a28d5d957623aa7b4aeda35ab5130e2c9.diff
LOG: [clang] Use current rounding mode for float inc/dec (#73770)
Increment and decrement are equivalent to adding or subtracting 1. For
the floating-point values these operations depend on the current
rounding mode. Teach constant evaluator to perform ++ and -- according
to the current floating-point environment.
Pull request: https://github.com/llvm/llvm-project/pull/73770
Added:
Modified:
clang/lib/AST/ExprConstant.cpp
clang/test/SemaCXX/rounding-math.cpp
Removed:
################################################################################
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 16697e5f076a8f8..2aafe5bd5289fc2 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -4623,11 +4623,13 @@ struct IncDecSubobjectHandler {
if (Old) *Old = APValue(Value);
APFloat One(Value.getSemantics(), 1);
+ llvm::RoundingMode RM = getActiveRoundingMode(Info, E);
+ APFloat::opStatus St;
if (AccessKind == AK_Increment)
- Value.add(One, APFloat::rmNearestTiesToEven);
+ St = Value.add(One, RM);
else
- Value.subtract(One, APFloat::rmNearestTiesToEven);
- return true;
+ St = Value.subtract(One, RM);
+ return checkFloatingPointResult(Info, E, St);
}
bool foundPointer(APValue &Subobj, QualType SubobjType) {
if (!checkConst(SubobjType))
diff --git a/clang/test/SemaCXX/rounding-math.cpp b/clang/test/SemaCXX/rounding-math.cpp
index 73f9f10e6d59417..e7ead05041b560d 100644
--- a/clang/test/SemaCXX/rounding-math.cpp
+++ b/clang/test/SemaCXX/rounding-math.cpp
@@ -77,3 +77,24 @@ struct S1d {
int f;
};
static_assert(sizeof(S1d) == sizeof(int), "");
+
+constexpr float incr_down(float k) {
+ float x = k;
+ ++x;
+ return x;
+}
+
+// 0x1.0p23 = 8388608.0, inc(8388608.0) = 8388609.0
+static_assert(incr_down(0x1.0p23F) == 0x1.000002p23F, "");
+// 0x1.0p24 = 16777216.0, inc(16777216.0) = 16777217.0 -> round down -> 16777216.0
+static_assert(incr_down(0x1.0p24F) == 0x1.0p24F, "");
+
+#pragma STDC FENV_ROUND FE_UPWARD
+constexpr float incr_up(float k) {
+ float x = k;
+ ++x;
+ return x;
+}
+static_assert(incr_up(0x1.0p23F) == 0x1.000002p23F, "");
+// 0x1.0p24 = 16777216.0, inc(16777216.0) = 16777217.0 -> round up -> 16777218.0
+static_assert(incr_up(0x1.0p24F) == 0x1.000002p24F, "");
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