From c67b6f268397b2fc20e72da19e276d2b027ddee4 Mon Sep 17 00:00:00 2001 From: Wilco Dijkstra Date: Fri, 16 Dec 2016 12:59:41 +0000 Subject: [PATCH] Thumb uses a special register allocation order to increase the use of low registers. Thumb uses a special register allocation order to increase the use of low registers. Oddly enough, LR appears before R12, which means that LR must be saved and restored even if R12 is available. Swapping R12 and LR means this simple example now uses R12 as a temporary (just like ARM): int f(long long a, long long b) { if (a < b) return 1; return a + b; } gcc/ * config/arm/arm.c (thumb_core_reg_alloc_order): Swap R12 and R14. From-SVN: r243744 --- gcc/ChangeLog | 4 ++++ gcc/config/arm/arm.c | 2 +- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 003f0120607..daa0458c6f2 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,7 @@ +2016-12-16 Wilco Dijkstra + + * config/arm/arm.c (thumb_core_reg_alloc_order): Swap R12 and R14. + 2016-12-16 Claudiu Zissulescu * config/arc/arc.md (call_prof): Remove. diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c index 899c001bf89..d0104f99a2e 100644 --- a/gcc/config/arm/arm.c +++ b/gcc/config/arm/arm.c @@ -27633,7 +27633,7 @@ arm_mangle_type (const_tree type) static const int thumb_core_reg_alloc_order[] = { 3, 2, 1, 0, 4, 5, 6, 7, - 14, 12, 8, 9, 10, 11 + 12, 14, 8, 9, 10, 11 }; /* Adjust register allocation order when compiling for Thumb. */ -- 2.30.2