Fix ppcf128 component access on little-endian systems
The PowerPC 128-bit long double data type (ppcf128 in LLVM) is in fact a
pair of two doubles, where one is considered the "high" or
more-significant part, and the other is considered the "low" or
less-significant part. When a ppcf128 value is stored in memory or a
register pair, the high part always comes first, i.e. at the lower
memory address or in the lower-numbered register, and the low part
always comes second. This is true both on big-endian and little-endian
PowerPC systems. (Similar to how with a complex number, the real part
always comes first and the imaginary part second, no matter the byte
order of the system.)
This was implemented incorrectly for little-endian systems in LLVM.
This commit fixes three related issues:
- When printing an immediate ppcf128 constant to assembler output
in emitGlobalConstantFP, emit the high part first on both big-
and little-endian systems.
- When lowering a ppcf128 type to a pair of f64 types in SelectionDAG
(which is used e.g. when generating code to load an argument into a
register pair), use correct low/high part ordering on little-endian
systems.
- In a related issue, because lowering ppcf128 into a pair of f64 must
operate differently from lowering an int128 into a pair of i64,
bitcasts between ppcf128 and int128 must not be optimized away by the
DAG combiner on little-endian systems, but must effect a word-swap.
Reviewed by Hal Finkel.
llvm-svn: 212274
diff --git a/llvm/test/CodeGen/X86/float-asmprint.ll b/llvm/test/CodeGen/X86/float-asmprint.ll
index 4aeae7f..5de9700 100644
--- a/llvm/test/CodeGen/X86/float-asmprint.ll
+++ b/llvm/test/CodeGen/X86/float-asmprint.ll
@@ -16,8 +16,9 @@
; CHECK-NEXT: .size
; CHECK: varppc128:
-; CHECK-NEXT: .quad 0 # ppc_fp128 -0
-; CHECK-NEXT: .quad -9223372036854775808
+; For ppc_fp128, the high double always comes first.
+; CHECK-NEXT: .quad -9223372036854775808 # ppc_fp128 -0
+; CHECK-NEXT: .quad 0
; CHECK-NEXT: .size
; CHECK: var80: