Remove wrong warning. Fix for https://github.com/llvm/llvm-project/issues/54625

[zahiraam]

Summary

When driver's floating-point options change, the user is made aware via a diagnostic. In the case of combining a fast math option with a non-fast option there should be no diagnostic. This patch removes the wrong diagnostic.
This is a fix for https://github.com/llvm/llvm-project/issues/54625.

[MaskRay]

Remove wrong warning. Fix for https://github.com/llvm/llvm-project/issues/54625

It's sufficient to reference https://github.com/llvm/llvm-project/issues/54625 in the commit message body.
For the subject line, just use some shorter IDs, e.g. issue 54625

It's somewhat conventional to use [Driver] tag for clang/lib/Driver changes.

clang/lib/Driver/ToolChains/Clang.cpp

case options::OPT_fno_fast_math:
       SignedZeros = true;
       // -fno_fast_math restores default denormal and fpcontract handling
       DenormalFPMath = DefaultDenormalFPMath;
       DenormalFP32Math = llvm::DenormalMode::getIEEE();
       if (!JA.isDeviceOffloading(Action::OFK_Cuda) &&
           !JA.isOffloading(Action::OFK_HIP))
         if (FPContract == "fast") {
           FPContract = "on";
-          D.Diag(clang::diag::warn_drv_overriding_flag_option)
-              << "-ffp-contract=fast"
-              << "-ffp-contract=on";
         }
       break;
     }
     if (StrictFPModel) {
       // If -ffp-model=strict has been specified on command line but
       // subsequent options conflict then emit warning diagnostic.
       if (HonorINFs && HonorNaNs && !AssociativeMath && !ReciprocalMath &&
           SignedZeros && TrappingMath && RoundingFPMath && !ApproxFunc &&

clang/test/Driver/fp-model.c

 // Test that incompatible combinations of -ffp-model= options
 // and other floating point options get a warning diagnostic.
 //
 // REQUIRES: clang-driver
 
+// expected-no-diagnostics
+
 // RUN: %clang -### -ffp-model=fast -ffp-contract=off -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARN %s
 // WARN: warning: overriding '-ffp-model=fast' option with '-ffp-contract=off' [-Woverriding-t-option]
 
 // RUN: %clang -### -ffp-model=fast -ffp-contract=on -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARN1 %s
 // WARN1: warning: overriding '-ffp-model=fast' option with '-ffp-contract=on' [-Woverriding-t-option]
 
 // RUN: %clang -### -ffp-model=strict -fassociative-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARN2 %s
 // WARN2: warning: overriding '-ffp-model=strict' option with '-fassociative-math' [-Woverriding-t-option]
 
 // RUN: %clang -### -ffp-model=strict -ffast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARN3 %s
 // WARN3: warning: overriding '-ffp-model=strict' option with '-ffast-math' [-Woverriding-t-option]
 
+// RUN: %clang -c -ffast-math -fno-fast-math -Xclang -verify %s 2>&1
+// RUN: %clang -c -fno-fast-math -ffast-math -Xclang -verify %s 2>&1
+// RUN: %clang -c -ffast-math -ffp-contract=on -Xclang -verify %s 2>&1
+// RUN: %clang -c -ffp-contract=on -ffast-math -Xclang -verify %s 2>&1
+// RUN: %clang -c -ffp-contract=on -ffp-model=fast -Xclang -verify %s 2>&1
+// RUN: %clang -c -ffp-model=fast -ffp-contract=on -Xclang -verify %s 2>&1
+
 // RUN: %clang -### -ffp-model=strict -ffinite-math-only -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARN4 %s
 // WARN4: warning: overriding '-ffp-model=strict' option with '-ffinite-math-only' [-Woverriding-t-option]
 
 // RUN: %clang -### -ffp-model=strict -ffp-contract=fast -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARN5 %s
 // WARN5: warning: overriding '-ffp-model=strict' option with '-ffp-contract=fast' [-Woverriding-t-option]
 

 // RUN: %clang -### -ffp-model=strict -funsafe-math-optimizations -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARNe %s
 // WARNe: warning: overriding '-ffp-model=strict' option with '-funsafe-math-optimizations' [-Woverriding-t-option]
 
 // RUN: %clang -### -ffp-model=strict -Ofast -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=WARNf %s
 // WARNf: warning: overriding '-ffp-model=strict' option with '-Ofast' [-Woverriding-t-option]
 
+// RUN: %clang -c -Ofast -fno-fast-math -Xclang -verify %s 2>&1
+// RUN: %clang -c -fno-fast-math -Ofast  -Xclang -verify %s 2>&1
+
 // RUN: %clang -### -ffp-model=strict -fdenormal-fp-math=preserve-sign,preserve-sign -c %s 2>&1 \
 // 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 -### -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NOROUND %s
 // CHECK-NOROUND: "-cc1"
 // CHECK-NOROUND: "-fno-rounding-math"

 // CHECK-FPM-FAST: "-ffinite-math-only"
 
 // RUN: %clang -### -nostdinc -ffp-model=precise -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FPM-PRECISE %s
 // CHECK-FPM-PRECISE: "-cc1"
 // CHECK-FPM-PRECISE: "-ffp-contract=on"
 // CHECK-FPM-PRECISE: "-fno-rounding-math"
 
+// RUN: %clang -c -ffp-model=precise -ffp-contract=fast -Xclang -verify %s 2>&1
+// RUN: %clang -c -ffp-contract=fast -ffp-model=precise -Xclang -verify %s 2>&1
+
 // RUN: %clang -### -nostdinc -ffp-model=strict -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FPM-STRICT %s
 // CHECK-FPM-STRICT: "-cc1"
 // CHECK-FPM-STRICT: "-frounding-math"
 // CHECK-FPM-STRICT: "-ffp-exception-behavior=strict"
 
 
 // RUN: %clang -### -nostdinc -ffp-exception-behavior=strict -c %s 2>&1 \