[PATCH] D66078: Added RAII object for authomatic restore of fp state

[Serge Pavlov via Phabricator via llvm-commits]

sepavloff created this revision.
sepavloff added reviewers: rjmccall, kpn, andrew.w.kaylor.
Herald added a project: LLVM.

Class IRBuilderBase has now RAII class that helps to restore floating
point options, including default rounding and exceptions modes.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D66078

Files:
  llvm/include/llvm/IR/IRBuilder.h
  llvm/include/llvm/IR/IntrinsicInst.h


Index: llvm/include/llvm/IR/IntrinsicInst.h
===================================================================
--- llvm/include/llvm/IR/IntrinsicInst.h
+++ llvm/include/llvm/IR/IntrinsicInst.h
@@ -212,11 +212,11 @@
     /// when constrained floating point is enabled. See the LLVM Language
     /// Reference Manual for details.
     enum RoundingMode : uint8_t {
-      rmDynamic,         ///< This corresponds to "fpround.dynamic".
       rmToNearest,       ///< This corresponds to "fpround.tonearest".
       rmDownward,        ///< This corresponds to "fpround.downward".
       rmUpward,          ///< This corresponds to "fpround.upward".
-      rmTowardZero       ///< This corresponds to "fpround.tozero".
+      rmTowardZero,      ///< This corresponds to "fpround.tozero".
+      rmDynamic          ///< This corresponds to "fpround.dynamic".
     };
 
     /// Specifies the required exception behavior. This is only used when
Index: llvm/include/llvm/IR/IRBuilder.h
===================================================================
--- llvm/include/llvm/IR/IRBuilder.h
+++ llvm/include/llvm/IR/IRBuilder.h
@@ -96,8 +96,14 @@
   MDNode *DefaultFPMathTag;
   FastMathFlags FMF;
 
+  /// If set, builder creates constrained floating point operations.
   bool IsFPConstrained;
+
+  /// Exception behavior used by default for constrained floating point
+  /// operations.
   ConstrainedFPIntrinsic::ExceptionBehavior DefaultConstrainedExcept;
+
+  /// Rounding mode used by default for constrained floating point operations.
   ConstrainedFPIntrinsic::RoundingMode DefaultConstrainedRounding;
 
   ArrayRef<OperandBundleDef> DefaultOperandBundles;
@@ -301,6 +307,36 @@
     }
   };
 
+  // RAII object that stores constrained floating point settings and
+  // restores them when the object is destroyed.
+  class FloatingPointStateSaver {
+    IRBuilderBase &Builder;
+    bool IsFPConstrainted;
+    ConstrainedFPIntrinsic::ExceptionBehavior DefaultConstrainedExcept;
+    ConstrainedFPIntrinsic::RoundingMode DefaultConstrainedRounding;
+
+  public:
+    FloatingPointStateSaver(IRBuilderBase &Builder)
+        : Builder(Builder),
+          IsFPConstrainted(Builder.getIsFPConstrained()),
+          DefaultConstrainedExcept(Builder.getDefaultConstrainedExcept()),
+          DefaultConstrainedRounding(Builder.getDefaultConstrainedRounding()) {
+    }
+    FloatingPointStateSaver(IRBuilderBase &Builder, bool NewIsFPConstrained,
+        ConstrainedFPIntrinsic::ExceptionBehavior NewDefaultConstrainedExcept,
+        ConstrainedFPIntrinsic::RoundingMode NewDefaultConstrainedRounding)
+        : FloatingPointStateSaver(Builder) {
+      Builder.setIsFPConstrained(NewIsFPConstrained);
+      Builder.setDefaultConstrainedExcept(NewDefaultConstrainedExcept);
+      Builder.setDefaultConstrainedRounding(NewDefaultConstrainedRounding);
+    }
+    ~FloatingPointStateSaver() {
+      Builder.setDefaultConstrainedRounding(DefaultConstrainedRounding);
+      Builder.setDefaultConstrainedExcept(DefaultConstrainedExcept);
+      Builder.setIsFPConstrained(IsFPConstrainted);
+    }
+  };
+
   //===--------------------------------------------------------------------===//
   // Miscellaneous creation methods.
   //===--------------------------------------------------------------------===//


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