[llvm] 24ecfda - [APFloat] Fix uninitialized variable in IEEEFloat constructors

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2020-09-09T11:38:30+01:00
New Revision: 24ecfdac7b7d195795b6cb0e373cba8bfa7911f4

URL: https://github.com/llvm/llvm-project/commit/24ecfdac7b7d195795b6cb0e373cba8bfa7911f4
DIFF: https://github.com/llvm/llvm-project/commit/24ecfdac7b7d195795b6cb0e373cba8bfa7911f4.diff

LOG: [APFloat] Fix uninitialized variable in IEEEFloat constructors

Some constructors of IEEEFloat do not initialize member variable exponent.
Fix it by initializing exponent with the following values:

For NaNs, the `exponent` is `maxExponent+1`.
For Infinities, the `exponent` is `maxExponent+1`.
For Zeroes, the `exponent` is `maxExponent-1`.

Patch by: @nullptr.cpp (Yang Fan)

Differential Revision: https://reviews.llvm.org/D86997

Added: 
    

Modified: 
    llvm/include/llvm/ADT/APFloat.h
    llvm/lib/Support/APFloat.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/APFloat.h b/llvm/include/llvm/ADT/APFloat.h
index 876e52c150a0..1f9ac22621a6 100644
--- a/llvm/include/llvm/ADT/APFloat.h
+++ b/llvm/include/llvm/ADT/APFloat.h
@@ -249,7 +249,7 @@ class IEEEFloat final : public APFloatBase {
   /// \name Constructors
   /// @{
 
-  IEEEFloat(const fltSemantics &); // Default construct to 0.0
+  IEEEFloat(const fltSemantics &); // Default construct to +0.0
   IEEEFloat(const fltSemantics &, integerPart);
   IEEEFloat(const fltSemantics &, uninitializedTag);
   IEEEFloat(const fltSemantics &, const APInt &);
@@ -539,6 +539,9 @@ class IEEEFloat final : public APFloatBase {
                                  roundingMode) const;
   opStatus roundSignificandWithExponent(const integerPart *, unsigned int, int,
                                         roundingMode);
+  ExponentType exponentNaN() const;
+  ExponentType exponentInf() const;
+  ExponentType exponentZero() const;
 
   /// @}
 

diff  --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index 569cac790af9..7a4c8bd3639d 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -755,6 +755,7 @@ void IEEEFloat::copySignificand(const IEEEFloat &rhs) {
 void IEEEFloat::makeNaN(bool SNaN, bool Negative, const APInt *fill) {
   category = fcNaN;
   sign = Negative;
+  exponent = exponentNaN();
 
   integerPart *significand = significandParts();
   unsigned numParts = partCount();
@@ -925,8 +926,7 @@ IEEEFloat::IEEEFloat(const fltSemantics &ourSemantics, integerPart value) {
 
 IEEEFloat::IEEEFloat(const fltSemantics &ourSemantics) {
   initialize(&ourSemantics);
-  category = fcZero;
-  sign = false;
+  makeZero(false);
 }
 
 // Delegate to the previous constructor, because later copy constructor may
@@ -3379,15 +3379,13 @@ void IEEEFloat::initFromF80LongDoubleAPInt(const APInt &api) {
 
   sign = static_cast<unsigned int>(i2>>15);
   if (myexponent == 0 && mysignificand == 0) {
-    // exponent, significand meaningless
-    category = fcZero;
+    makeZero(sign);
   } else if (myexponent==0x7fff && mysignificand==0x8000000000000000ULL) {
-    // exponent, significand meaningless
-    category = fcInfinity;
+    makeInf(sign);
   } else if ((myexponent == 0x7fff && mysignificand != 0x8000000000000000ULL) ||
              (myexponent != 0x7fff && myexponent != 0 && myintegerbit == 0)) {
-    // exponent meaningless
     category = fcNaN;
+    exponent = exponentNaN();
     significandParts()[0] = mysignificand;
     significandParts()[1] = 0;
   } else {
@@ -3438,16 +3436,14 @@ void IEEEFloat::initFromQuadrupleAPInt(const APInt &api) {
   sign = static_cast<unsigned int>(i2>>63);
   if (myexponent==0 &&
       (mysignificand==0 && mysignificand2==0)) {
-    // exponent, significand meaningless
-    category = fcZero;
+    makeZero(sign);
   } else if (myexponent==0x7fff &&
              (mysignificand==0 && mysignificand2==0)) {
-    // exponent, significand meaningless
-    category = fcInfinity;
+    makeInf(sign);
   } else if (myexponent==0x7fff &&
              (mysignificand!=0 || mysignificand2 !=0)) {
-    // exponent meaningless
     category = fcNaN;
+    exponent = exponentNaN();
     significandParts()[0] = mysignificand;
     significandParts()[1] = mysignificand2;
   } else {
@@ -3473,14 +3469,12 @@ void IEEEFloat::initFromDoubleAPInt(const APInt &api) {
 
   sign = static_cast<unsigned int>(i>>63);
   if (myexponent==0 && mysignificand==0) {
-    // exponent, significand meaningless
-    category = fcZero;
+    makeZero(sign);
   } else if (myexponent==0x7ff && mysignificand==0) {
-    // exponent, significand meaningless
-    category = fcInfinity;
+    makeInf(sign);
   } else if (myexponent==0x7ff && mysignificand!=0) {
-    // exponent meaningless
     category = fcNaN;
+    exponent = exponentNaN();
     *significandParts() = mysignificand;
   } else {
     category = fcNormal;
@@ -3504,14 +3498,12 @@ void IEEEFloat::initFromFloatAPInt(const APInt &api) {
 
   sign = i >> 31;
   if (myexponent==0 && mysignificand==0) {
-    // exponent, significand meaningless
-    category = fcZero;
+    makeZero(sign);
   } else if (myexponent==0xff && mysignificand==0) {
-    // exponent, significand meaningless
-    category = fcInfinity;
+    makeInf(sign);
   } else if (myexponent==0xff && mysignificand!=0) {
-    // sign, exponent, significand meaningless
     category = fcNaN;
+    exponent = exponentNaN();
     *significandParts() = mysignificand;
   } else {
     category = fcNormal;
@@ -3535,14 +3527,12 @@ void IEEEFloat::initFromBFloatAPInt(const APInt &api) {
 
   sign = i >> 15;
   if (myexponent == 0 && mysignificand == 0) {
-    // exponent, significand meaningless
-    category = fcZero;
+    makeZero(sign);
   } else if (myexponent == 0xff && mysignificand == 0) {
-    // exponent, significand meaningless
-    category = fcInfinity;
+    makeInf(sign);
   } else if (myexponent == 0xff && mysignificand != 0) {
-    // sign, exponent, significand meaningless
     category = fcNaN;
+    exponent = exponentNaN();
     *significandParts() = mysignificand;
   } else {
     category = fcNormal;
@@ -3566,14 +3556,12 @@ void IEEEFloat::initFromHalfAPInt(const APInt &api) {
 
   sign = i >> 15;
   if (myexponent==0 && mysignificand==0) {
-    // exponent, significand meaningless
-    category = fcZero;
+    makeZero(sign);
   } else if (myexponent==0x1f && mysignificand==0) {
-    // exponent, significand meaningless
-    category = fcInfinity;
+    makeInf(sign);
   } else if (myexponent==0x1f && mysignificand!=0) {
-    // sign, exponent, significand meaningless
     category = fcNaN;
+    exponent = exponentNaN();
     *significandParts() = mysignificand;
   } else {
     category = fcNormal;
@@ -4131,17 +4119,29 @@ IEEEFloat::opStatus IEEEFloat::next(bool nextDown) {
   return result;
 }
 
+APFloatBase::ExponentType IEEEFloat::exponentNaN() const {
+  return semantics->maxExponent + 1;
+}
+
+APFloatBase::ExponentType IEEEFloat::exponentInf() const {
+  return semantics->maxExponent + 1;
+}
+
+APFloatBase::ExponentType IEEEFloat::exponentZero() const {
+  return semantics->minExponent - 1;
+}
+
 void IEEEFloat::makeInf(bool Negative) {
   category = fcInfinity;
   sign = Negative;
-  exponent = semantics->maxExponent + 1;
+  exponent = exponentInf();
   APInt::tcSet(significandParts(), 0, partCount());
 }
 
 void IEEEFloat::makeZero(bool Negative) {
   category = fcZero;
   sign = Negative;
-  exponent = semantics->minExponent-1;
+  exponent = exponentZero();
   APInt::tcSet(significandParts(), 0, partCount());
 }