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f7819ce166
This is a recommit ofb822efc740, reverted indc34d8df4c. The commit caused fails because the test ast-print-fp-pragmas.c did not specify particular target, and it failed on targets which do not support constrained intrinsics. The original commit message is below. AST does not have special nodes for pragmas. Instead a pragma modifies some state variables of Sema, which in turn results in modified attributes of AST nodes. This technique applies to floating point operations as well. Every AST node that can depend on FP options keeps current set of them. This technique works well for options like exception behavior or fast math options. They represent instructions to the compiler how to modify code generation for the affected nodes. However treatment of FP control modes has problems with this technique. Modifying FP control mode (like rounding direction) usually requires operations on hardware, like writing to control registers. It must be done prior to the first operation that depends on the control mode. In particular, such operations are required for implementation of `pragma STDC FENV_ROUND`, compiler should set up necessary rounding direction at the beginning of compound statement where the pragma occurs. As there is no representation for pragmas in AST, the code generation becomes a complicated task in this case. To solve this issue FP options are kept inside CompoundStmt. Unlike to FP options in expressions, these does not affect any operation on FP values, but only inform the codegen about the FP options that act in the body of the statement. As all pragmas that modify FP environment may occurs only at the start of compound statement or at global level, such solution works for all relevant pragmas. The options are kept as a difference from the options in the enclosing compound statement or default options, it helps codegen to set only changed control modes. Differential Revision: https://reviews.llvm.org/D123952
70 lines
1.8 KiB
C
70 lines
1.8 KiB
C
// RUN: %clang_cc1 -fsyntax-only -triple x86_64-pc-linux -ast-print %s -o - | FileCheck %s
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float func_1(float x, float y) {
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#pragma STDC FENV_ACCESS ON
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if (x != 0) {
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return y;
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}
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return x + y;
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}
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// CHECK-LABEL: float func_1(float x, float y) {
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// CHECK-NEXT: #pragma STDC FENV_ACCESS ON
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// CHECK-NEXT: if (x != 0) {
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// CHECK-NEXT: return y;
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// CHECK-NEXT: }
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// CHECK-NEXT: return x + y;
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// CHECK-NEXT: }
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float func_2(float x, float y) {
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#pragma STDC FENV_ACCESS ON
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if (x != 0) {
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#pragma STDC FENV_ACCESS OFF
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return y;
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}
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return x + y;
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}
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// CHECK-LABEL: float func_2(float x, float y) {
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// CHECK-NEXT: #pragma STDC FENV_ACCESS ON
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// CHECK-NEXT: if (x != 0) {
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// CHECK-NEXT: #pragma STDC FENV_ACCESS OFF
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// CHECK-NEXT: return y;
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// CHECK-NEXT: }
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// CHECK-NEXT: return x + y;
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// CHECK-NEXT: }
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float func_3(float x, float y) {
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#pragma STDC FENV_ROUND FE_DOWNWARD
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return x + y;
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}
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// CHECK-LABEL: float func_3(float x, float y) {
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// CHECK-NEXT: #pragma STDC FENV_ROUND FE_DOWNWARD
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// CHECK-NEXT: return x + y;
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// CHECK-NEXT: }
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float func_4(float x, float y, float z) {
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#pragma STDC FENV_ACCESS ON
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#pragma clang fp exceptions(maytrap)
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#pragma STDC FENV_ROUND FE_UPWARD
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if (z != 0) {
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#pragma STDC FENV_ACCESS OFF
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#pragma STDC FENV_ROUND FE_TOWARDZERO
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return z + x;
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}
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return x + y;
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}
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// CHECK-LABEL: float func_4(float x, float y, float z) {
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// CHECK-NEXT: #pragma STDC FENV_ACCESS ON
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// CHECK-NEXT: #pragma clang fp exceptions(maytrap)
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// CHECK-NEXT: #pragma STDC FENV_ROUND FE_UPWARD
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// CHECK-NEXT: if (z != 0) {
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// CHECK-NEXT: #pragma STDC FENV_ACCESS OFF
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// CHECK-NEXT: #pragma STDC FENV_ROUND FE_TOWARDZERO
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// CHECK-NEXT: return z + x;
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// CHECK-NEXT: }
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// CHECK-NEXT: return x + y;
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// CHECK-NEXT: }
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