[llvm] cd9e1a0 - [Constants][PowerPC] Check exactlyValue for ppc_fp128 in isNullValue

[Jinsong Ji via llvm-commits]

Author: Jinsong Ji
Date: 2021-06-03T20:31:01Z
New Revision: cd9e1a020cf0902e79ae1178cc4b93f5c5ce9381

URL: https://github.com/llvm/llvm-project/commit/cd9e1a020cf0902e79ae1178cc4b93f5c5ce9381
DIFF: https://github.com/llvm/llvm-project/commit/cd9e1a020cf0902e79ae1178cc4b93f5c5ce9381.diff

LOG: [Constants][PowerPC] Check exactlyValue for ppc_fp128 in isNullValue

 PPC_FP128 determines isZero/isNan/isInf using high-order double value
 only. Checking isZero/isNegative might return the isNullValue unexpectedly.
 eg:
   0xM0000000000000000FFFFFFFFFFFFFFFFF

isZero, but it is not NullValue.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D103634

Added: 
    

Modified: 
    llvm/lib/IR/Constants.cpp
    llvm/test/CodeGen/PowerPC/ppc_fp128-bcwriter.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index 54b0a7d4826e3..c3134dc795a55 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -90,7 +90,9 @@ bool Constant::isNullValue() const {
 
   // +0.0 is null.
   if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
-    return CFP->isZero() && !CFP->isNegative();
+    // ppc_fp128 determine isZero using high order double only
+    // Should check the bitwise value to make sure all bits are zero.
+    return CFP->isExactlyValue(+0.0);
 
   // constant zero is zero for aggregates, cpnull is null for pointers, none for
   // tokens.

diff  --git a/llvm/test/CodeGen/PowerPC/ppc_fp128-bcwriter.ll b/llvm/test/CodeGen/PowerPC/ppc_fp128-bcwriter.ll
index 7bf361f52d2ae..101a0e49abdeb 100644
--- a/llvm/test/CodeGen/PowerPC/ppc_fp128-bcwriter.ll
+++ b/llvm/test/CodeGen/PowerPC/ppc_fp128-bcwriter.ll
@@ -1,7 +1,7 @@
 ; RUN: llvm-as < %s -o - | llvm-dis - | FileCheck %s
 
 ;CHECK-LABEL: main
-;CHECK: store ppc_fp128 0xM0000000000000000000000000000000
+;CHECK: store ppc_fp128 0xM0000000000000000FFFFFFFFFFFFFFFF
 
 define i32 @main() local_unnamed_addr {
 _main_entry: