0005-float-zero-v01.patch

From 4d642810ecb432520198cf7fe7e07f33fa2b61a7 Mon Sep 17 00:00:00 2001
From: Emre Hasegeli <emre@hasegeli.com>
Date: Thu, 2 Nov 2017 12:21:19 +0100
Subject: [PATCH 5/6] float-zero-v01

Check for float -0 after multiplications and divisions
---
 src/include/utils/float.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/include/utils/float.h b/src/include/utils/float.h
index c9f5fd30ca..021732d5c6 100644
--- a/src/include/utils/float.h
+++ b/src/include/utils/float.h
@@ -215,64 +215,76 @@ float8_mi(float8 val1, float8 val2)
 
 static inline float4
 float4_mul(float4 val1, float4 val2)
 {
 	float4		result;
 
 	result = val1 * val2;
 	check_float4_val(result, isinf(val1) || isinf(val2),
 					 val1 == 0.0f || val2 == 0.0f);
 
+	if (result == -0.0f)
+		result = 0.0f;
+
 	return result;
 }
 
 static inline float8
 float8_mul(float8 val1, float8 val2)
 {
 	float8		result;
 
 	result = val1 * val2;
 	check_float8_val(result, isinf(val1) || isinf(val2),
 					 val1 == 0.0 || val2 == 0.0);
 
+	if (result == -0.0)
+		result = 0.0;
+
 	return result;
 }
 
 static inline float4
 float4_div(float4 val1, float4 val2)
 {
 	float4		result;
 
 	if (val2 == 0.0f)
 		ereport(ERROR,
 				(errcode(ERRCODE_DIVISION_BY_ZERO),
 				 errmsg("division by zero")));
 
 	result = val1 / val2;
 	check_float4_val(result, isinf(val1) || isinf(val2), val1 == 0.0f);
 
+	if (result == -0.0f)
+		result = 0.0f;
+
 	return result;
 }
 
 static inline float8
 float8_div(float8 val1, float8 val2)
 {
 	float8		result;
 
 	if (val2 == 0.0)
 		ereport(ERROR,
 				(errcode(ERRCODE_DIVISION_BY_ZERO),
 				 errmsg("division by zero")));
 
 	result = val1 / val2;
 	check_float8_val(result, isinf(val1) || isinf(val2), val1 == 0.0);
 
+	if (result == -0.0)
+		result = 0.0;
+
 	return result;
 }
 
 /*
  * Routines for NaN-aware comparisons
  *
  * We consider all NANs to be equal and larger than any non-NAN. This is
  * somewhat arbitrary; the important thing is to have a consistent sort
  * order.
  */
-- 
2.13.6 (Apple Git-96)