sepavloff created this revision.
sepavloff added reviewers: rjmccall, aaron.ballman, kpn.
Herald added a project: All.
sepavloff requested review of this revision.
Herald added a project: clang.
Now starting from the first use of `pragma FENV_ROUND` rounding mode
becomes user-defined and there is no way to return back to initial
state. Default rounding mode and the same explicitly defined one result
in different AST. For example, the code:
float func_04(float x, float y) {
return x + y;
}
produces AST where the FP operation is represented with the node:
`-BinaryOperator 0x25d6e2cecb8 <col:10, col:14> 'float' '+'
The same code with `#pragma STDC FENV_ROUND FE_TONEAREST` before the
function definition produces slightly different representation:
`-BinaryOperator 0x1832c1a4ce8 <col:10, col:14> 'float' '+'
ConstRoundingMode=tonearest
Code generation is not changed in this case because `tonearest` is the
rounding mode in default FP environment. However if an AST object has
an override for a FP property, it considered as explicitly specified
and is preserved in some cases where default property may be overridden.
Default rounding mode is `dynamic` according to the C2x standard
draft (7.6.2p3):
... If no FENV_ROUND pragma is in effect, or the specified constant
rounding mode is FE_DYNAMIC, rounding is according to the mode
specified by the dynamic floating-point environment ...
So pragma `FENV_ROUND FE_DYNAMIC` must reset rounding to default state,
but now it only adds related override:
`-BinaryOperator 0x1cb8cfaaec8 <col:10, col:14> 'float' '+'
ConstRoundingMode=dynamic
This change fixes the pragma behavior. If `FENV_ROUND FE_DYNAMIC` is
specified without `FENV_ACCESS ON`, the rounding mode override is
removed, which effectively establish default rounding mode state.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D130907
Files:
clang/lib/Sema/SemaStmt.cpp
clang/test/AST/ast-dump-fpfeatures.cpp
Index: clang/test/AST/ast-dump-fpfeatures.cpp
===================================================================
--- clang/test/AST/ast-dump-fpfeatures.cpp
+++ clang/test/AST/ast-dump-fpfeatures.cpp
@@ -109,7 +109,18 @@
}
// CHECK-LABEL: FunctionDecl {{.*}} func_12 'float (float, float)'
+// CHECK: BinaryOperator {{.*}} 'float' '+'
+
+#pragma STDC FENV_ROUND FE_DYNAMIC
+#pragma STDC FENV_ACCESS ON
+
+float func_12a(float x, float y) {
+ return x + y;
+}
+
+// CHECK-LABEL: FunctionDecl {{.*}} func_12a 'float (float, float)'
// CHECK: BinaryOperator {{.*}} 'float' '+' ConstRoundingMode=dynamic
+#pragma STDC FENV_ACCESS OFF
#pragma STDC FENV_ROUND FE_TONEAREST
Index: clang/lib/Sema/SemaStmt.cpp
===================================================================
--- clang/lib/Sema/SemaStmt.cpp
+++ clang/lib/Sema/SemaStmt.cpp
@@ -391,7 +391,14 @@
}
void Sema::ActOnAfterCompoundStatementLeadingPragmas() {
- if (getCurFPFeatures().isFPConstrained()) {
+ FPOptions &FPO = getCurFPFeatures();
+ if (FPO.getConstRoundingMode() == llvm::RoundingMode::Dynamic &&
+ !FPO.getAllowFEnvAccess()) {
+ // If dynamic rounding mode is specified in absence of FENV_ACCESS, treat
it
+ // as setting default rounding mode.
+ FpPragmaStack.CurrentValue.clearConstRoundingModeOverride();
+ }
+ if (FPO.isFPConstrained()) {
FunctionScopeInfo *FSI = getCurFunction();
assert(FSI);
FSI->setUsesFPIntrin();
Index: clang/test/AST/ast-dump-fpfeatures.cpp
===================================================================
--- clang/test/AST/ast-dump-fpfeatures.cpp
+++ clang/test/AST/ast-dump-fpfeatures.cpp
@@ -109,7 +109,18 @@
}
// CHECK-LABEL: FunctionDecl {{.*}} func_12 'float (float, float)'
+// CHECK: BinaryOperator {{.*}} 'float' '+'
+
+#pragma STDC FENV_ROUND FE_DYNAMIC
+#pragma STDC FENV_ACCESS ON
+
+float func_12a(float x, float y) {
+ return x + y;
+}
+
+// CHECK-LABEL: FunctionDecl {{.*}} func_12a 'float (float, float)'
// CHECK: BinaryOperator {{.*}} 'float' '+' ConstRoundingMode=dynamic
+#pragma STDC FENV_ACCESS OFF
#pragma STDC FENV_ROUND FE_TONEAREST
Index: clang/lib/Sema/SemaStmt.cpp
===================================================================
--- clang/lib/Sema/SemaStmt.cpp
+++ clang/lib/Sema/SemaStmt.cpp
@@ -391,7 +391,14 @@
}
void Sema::ActOnAfterCompoundStatementLeadingPragmas() {
- if (getCurFPFeatures().isFPConstrained()) {
+ FPOptions &FPO = getCurFPFeatures();
+ if (FPO.getConstRoundingMode() == llvm::RoundingMode::Dynamic &&
+ !FPO.getAllowFEnvAccess()) {
+ // If dynamic rounding mode is specified in absence of FENV_ACCESS, treat it
+ // as setting default rounding mode.
+ FpPragmaStack.CurrentValue.clearConstRoundingModeOverride();
+ }
+ if (FPO.isFPConstrained()) {
FunctionScopeInfo *FSI = getCurFunction();
assert(FSI);
FSI->setUsesFPIntrin();
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
