From 8fbe4ddc7c7269ebe87e774693dc12d5b29f7d83 Mon Sep 17 00:00:00 2001 From: Ricky Taylor Date: Thu, 26 Aug 2021 22:13:28 +0100 Subject: [PATCH] [M68k] Update pointer data layout Fixes PR51626. The M68k requires that all instruction, word and long word reads are aligned to word boundaries. From the 68020 onwards, there is a performance benefit from aligning long words to long word boundaries. The M68k uses the same data layout for pointers and integers. In line with this, this commit updates the pointer data layout to match the layout already set for 32-bit integers: 32:16:32. Differential Revision: https://reviews.llvm.org/D108792 (cherry picked from commit 8d3f112f0cdbed2311aead86bcd72e763ad55255) --- lib/Target/M68k/M68kTargetMachine.cpp | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/lib/Target/M68k/M68kTargetMachine.cpp b/lib/Target/M68k/M68kTargetMachine.cpp index 5b8fd3d41b1..cb7d8f8b25e 100644 --- a/lib/Target/M68k/M68kTargetMachine.cpp +++ b/lib/Target/M68k/M68kTargetMachine.cpp @@ -49,10 +49,14 @@ std::string computeDataLayout(const Triple &TT, StringRef CPU, // FIXME how to wire it with the used object format? Ret += "-m:e"; - // M68k pointers are always 32 bit wide even for 16 bit cpus - Ret += "-p:32:32"; + // M68k pointers are always 32 bit wide even for 16-bit CPUs. + // The ABI only specifies 16-bit alignment. + // On at least the 68020+ with a 32-bit bus, there is a performance benefit + // to having 32-bit alignment. + Ret += "-p:32:16:32"; - // M68k requires i8 to align on 2 byte boundry + // Bytes do not require special alignment, words are word aligned and + // long words are word aligned at minimum. Ret += "-i8:8:8-i16:16:16-i32:16:32"; // FIXME no floats at the moment