[flang-commits] [flang] 956cf0e - [flang][OpenMP] Fix min reduction initialization (#73102)

[via flang-commits]

Author: NimishMishra
Date: 2023-11-22T03:40:18-08:00
New Revision: 956cf0e5de4b816ccba64206ead8bc2d4fd22158

URL: https://github.com/llvm/llvm-project/commit/956cf0e5de4b816ccba64206ead8bc2d4fd22158
DIFF: https://github.com/llvm/llvm-project/commit/956cf0e5de4b816ccba64206ead8bc2d4fd22158.diff

LOG: [flang][OpenMP] Fix min reduction initialization (#73102)

Initialization of reduction variable for min-reduction is set to largest
negative value. As such, in presence of non-negative operands, min
reduction gives incorrect output. This patch initialises min-reduction
to use the maximum positive value instead, so that it can produce
correct output for the entire range of real valued operands.

Fixes https://github.com/llvm/llvm-project/issues/73101

Added: 
    

Modified: 
    flang/lib/Lower/OpenMP.cpp
    flang/test/Lower/OpenMP/FIR/wsloop-reduction-min.f90
    flang/test/Lower/OpenMP/wsloop-reduction-min.f90

Removed: 
    


################################################################################
diff  --git a/flang/lib/Lower/OpenMP.cpp b/flang/lib/Lower/OpenMP.cpp
index 517812305358c77..f6a61ba3a528e32 100644
--- a/flang/lib/Lower/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP.cpp
@@ -754,7 +754,7 @@ static mlir::Value getReductionInitValue(mlir::Location loc, mlir::Type type,
     if (auto ty = type.dyn_cast<mlir::FloatType>()) {
       const llvm::fltSemantics &sem = ty.getFloatSemantics();
       return builder.createRealConstant(
-          loc, type, llvm::APFloat::getSmallest(sem, /*Negative=*/true));
+          loc, type, llvm::APFloat::getLargest(sem, /*Negative=*/false));
     }
     unsigned bits = type.getIntOrFloatBitWidth();
     int64_t maxInt = llvm::APInt::getSignedMaxValue(bits).getSExtValue();

diff  --git a/flang/test/Lower/OpenMP/FIR/wsloop-reduction-min.f90 b/flang/test/Lower/OpenMP/FIR/wsloop-reduction-min.f90
index 880d94b910af976..22cdd41c95179bd 100644
--- a/flang/test/Lower/OpenMP/FIR/wsloop-reduction-min.f90
+++ b/flang/test/Lower/OpenMP/FIR/wsloop-reduction-min.f90
@@ -2,7 +2,7 @@
 ! RUN: %flang_fc1 -emit-fir -flang-deprecated-no-hlfir -fopenmp -o - %s 2>&1 | FileCheck %s
 
 !CHECK: omp.reduction.declare @[[MIN_DECLARE_F:.*]] : f32 init {
-!CHECK:   %[[MAXIMUM_VAL_F:.*]] = arith.constant -1.401300e-45 : f32
+!CHECK:   %[[MAXIMUM_VAL_F:.*]] = arith.constant 3.40282347E+38 : f32
 !CHECK:   omp.yield(%[[MAXIMUM_VAL_F]] : f32)
 !CHECK: combiner
 !CHECK: ^bb0(%[[ARG0_F:.*]]: f32, %[[ARG1_F:.*]]: f32):

diff  --git a/flang/test/Lower/OpenMP/wsloop-reduction-min.f90 b/flang/test/Lower/OpenMP/wsloop-reduction-min.f90
index c1c91122efddc63..af7f718b0b26d05 100644
--- a/flang/test/Lower/OpenMP/wsloop-reduction-min.f90
+++ b/flang/test/Lower/OpenMP/wsloop-reduction-min.f90
@@ -2,7 +2,7 @@
 ! RUN: %flang_fc1 -emit-hlfir -fopenmp -o - %s 2>&1 | FileCheck %s
 
 !CHECK: omp.reduction.declare @[[MIN_DECLARE_F:.*]] : f32 init {
-!CHECK:   %[[MAXIMUM_VAL_F:.*]] = arith.constant -1.401300e-45 : f32
+!CHECK:   %[[MAXIMUM_VAL_F:.*]] = arith.constant 3.40282347E+38 : f32
 !CHECK:   omp.yield(%[[MAXIMUM_VAL_F]] : f32)
 !CHECK: combiner
 !CHECK: ^bb0(%[[ARG0_F:.*]]: f32, %[[ARG1_F:.*]]: f32):