[PATCH] D137618: [Clang] Fix behavior of -ffp-model option when overriden

[Qiu Chaofan via Phabricator via cfe-commits]

qiucf created this revision.
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`-ffp-model=strict -ffp-model=fast` will still enable strict exception handling behavior, therefore clang still emits constrained FP operations in IR.

`-ffp-model=fast -ffp-model=strict` emits two warnings: one for `strict` overriding `fast`, the other for `strict` overriding `strict`, which is confusing.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D137618

Files:
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/test/Driver/fp-model.c


Index: clang/test/Driver/fp-model.c
===================================================================
--- clang/test/Driver/fp-model.c
+++ clang/test/Driver/fp-model.c
@@ -66,6 +66,11 @@
 // RUN:   | FileCheck --check-prefix=WARN10 %s
 // WARN10: warning: overriding '-ffp-model=strict' option with '-fdenormal-fp-math=preserve-sign,preserve-sign' [-Woverriding-t-option]
 
+// RUN: %clang -### -ffp-model=fast -ffp-model=strict -c %s 2>&1 | FileCheck \
+// RUN:   --check-prefix=WARN11 %s
+// WARN11: warning: overriding '-ffp-model=fast' option with '-ffp-model=strict' [-Woverriding-t-option]
+// WARN11-NOT: warning: overriding '-ffp-model=strict' option with '-ffp-model=strict' [-Woverriding-t-option]
+
 // RUN: %clang -### -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NOROUND %s
 // CHECK-NOROUND: "-cc1"
@@ -107,6 +112,9 @@
 // CHECK-FPM-STRICT: "-frounding-math"
 // CHECK-FPM-STRICT: "-ffp-exception-behavior=strict"
 
+// RUN: %clang -### -nostdinc -ffp-model=strict -ffp-model=fast -c %s 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NO-EXCEPT %s
+// CHECK-NO-EXCEPT-NOT: "-ffp-exception-behavior=strict"
 
 // RUN: %clang -### -nostdinc -ffp-exception-behavior=strict -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FEB-STRICT %s
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -2841,6 +2841,7 @@
         optID = options::OPT_ffast_math;
         FPModel = Val;
         FPContract = "fast";
+        FPExceptionBehavior = "";
       } else if (Val.equals("precise")) {
         optID = options::OPT_ffp_contract;
         FPModel = Val;
@@ -3071,10 +3072,12 @@
       else {
         StrictFPModel = false;
         FPModel = "";
-        D.Diag(clang::diag::warn_drv_overriding_flag_option)
-            << "-ffp-model=strict" <<
-            ((A->getNumValues() == 0) ?  A->getSpelling()
-            : Args.MakeArgString(A->getSpelling() + A->getValue()));
+        auto RHS = (A->getNumValues() == 0)
+                       ? A->getSpelling()
+                       : Args.MakeArgString(A->getSpelling() + A->getValue());
+        if (RHS != "-ffp-model=strict")
+          D.Diag(clang::diag::warn_drv_overriding_flag_option)
+              << "-ffp-model=strict" << RHS;
       }
     }
 


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