From afaff4016408eb02109e41ee5f171c928dafe2a8 Mon Sep 17 00:00:00 2001
From: Jeff Genovy <jefgen@microsoft.com>
Date: Mon, 25 Nov 2019 17:07:47 -0800
Subject: [PATCH] ICU-20907 Disable optimization on Windows when building for
 ARM64 with Visual Studio versions below 16.4.

---
 icu4c/source/common/normalizer2impl.cpp | 10 ++++++++++
 icu4c/source/common/ubidiwrt.cpp        | 10 ++++++++++
 2 files changed, 20 insertions(+)

diff --git a/icu4c/source/common/normalizer2impl.cpp b/icu4c/source/common/normalizer2impl.cpp
index b2dd7ad4b8..cbf6b4d980 100644
--- a/icu4c/source/common/normalizer2impl.cpp
+++ b/icu4c/source/common/normalizer2impl.cpp
@@ -2088,6 +2088,13 @@ uint8_t Normalizer2Impl::getPreviousTrailCC(const uint8_t *start, const uint8_t
 // minDecompNoCP etc. and smallFCD[] are intended to help with any loss of performance,
 // at least for ASCII & CJK.
 
+// Ticket 20907 - The optimizer in MSVC/Visual Studio versions below 16.4 has trouble with this
+// function on Windows ARM64. As a work-around, we disable optimizations for this function.
+// This work-around could/should be removed once the following versions of Visual Studio are no
+// longer supported: All versions of VS2017, and versions of VS2019 below 16.4.
+#if (defined(_MSC_VER) && (defined(_M_ARM64)) && (_MSC_VER < 1924))
+#pragma optimize( "", off )
+#endif
 // Gets the FCD value from the regular normalization data.
 uint16_t Normalizer2Impl::getFCD16FromNormData(UChar32 c) const {
     uint16_t norm16=getNorm16(c);
@@ -2121,6 +2128,9 @@ uint16_t Normalizer2Impl::getFCD16FromNormData(UChar32 c) const {
     }
     return norm16;
 }
+#if (defined(_MSC_VER) && (defined(_M_ARM64)) && (_MSC_VER < 1924))
+#pragma optimize( "", on )
+#endif
 
 // Dual functionality:
 // buffer!=NULL: normalize
diff --git a/icu4c/source/common/ubidiwrt.cpp b/icu4c/source/common/ubidiwrt.cpp
index aa4d6b544c..a69c0a4b8b 100644
--- a/icu4c/source/common/ubidiwrt.cpp
+++ b/icu4c/source/common/ubidiwrt.cpp
@@ -346,6 +346,13 @@ ubidi_writeReverse(const UChar *src, int32_t srcLength,
     return u_terminateUChars(dest, destSize, destLength, pErrorCode);
 }
 
+// Ticket 20907 - The optimizer in MSVC/Visual Studio versions below 16.4 has trouble with this
+// function on Windows ARM64. As a work-around, we disable optimizations for this function.
+// This work-around could/should be removed once the following versions of Visual Studio are no
+// longer supported: All versions of VS2017, and versions of VS2019 below 16.4.
+#if (defined(_MSC_VER) && (defined(_M_ARM64)) && (_MSC_VER < 1924))
+#pragma optimize( "", off )
+#endif
 U_CAPI int32_t U_EXPORT2
 ubidi_writeReordered(UBiDi *pBiDi,
                      UChar *dest, int32_t destSize,
@@ -638,3 +645,6 @@ ubidi_writeReordered(UBiDi *pBiDi,
 
     return u_terminateUChars(saveDest, destCapacity, destCapacity-destSize, pErrorCode);
 }
+#if (defined(_MSC_VER) && (defined(_M_ARM64)) && (_MSC_VER < 1924))
+#pragma optimize( "", on )
+#endif