[ARM] Honour ABI for rem under -O0 for EABI, GNUEABI, Android and Musl
At higher optimization levels, we generate the libcall for DIVREM_Ix, which is
fine: aeabi_{u|i}divmod. At -O0 we generate the one for REM_Ix, which is the
default {u}mod{q|h|s|d}i3.
This commit makes sure that we don't generate REM_Ix calls for ABIs that
don't support them (i.e. where we need to use DIVREM_Ix instead). This is
achieved by bailing out of FastISel, which can't handle non-double multi-reg
returns, and letting the legalization infrastructure expand the REM_Ix calls.
It also updates the divmod-eabi.ll test to run under -O0 as well, and adds some
Windows checks to it to make sure we don't break things for it.
Fixes PR27068
Differential Revision: https://reviews.llvm.org/D21926
llvm-svn: 275773
diff --git a/llvm/lib/Target/ARM/ARMFastISel.cpp b/llvm/lib/Target/ARM/ARMFastISel.cpp
index 0f11ac9..13724da 100644
--- a/llvm/lib/Target/ARM/ARMFastISel.cpp
+++ b/llvm/lib/Target/ARM/ARMFastISel.cpp
@@ -1718,6 +1718,13 @@
if (!isTypeLegal(Ty, VT))
return false;
+ // Many ABIs do not provide a libcall for standalone remainder, so we need to
+ // use divrem (see the RTABI 4.3.1). Since FastISel can't handle non-double
+ // multi-reg returns, we'll have to bail out.
+ if (!TLI.hasStandaloneRem(VT)) {
+ return false;
+ }
+
RTLIB::Libcall LC = RTLIB::UNKNOWN_LIBCALL;
if (VT == MVT::i8)
LC = isSigned ? RTLIB::SREM_I8 : RTLIB::UREM_I8;