[mips] Optimize stack pointer adjustments.
Instead of always using addu to adjust the stack pointer when the
size out is of the range of an addiu instruction, use subu so that
a smaller constant can be generated.
This can give savings of ~3 instructions whenever a function has a
a stack frame whose size is out of range of an addiu instruction.
This change may break some naive stack unwinders.
Partially resolves PR/26291.
Thanks to David Chisnall for reporting the issue.
Reviewers: dsanders, vkalintiris
Differential Review: http://reviews.llvm.org/D21321
llvm-svn: 272666
diff --git a/llvm/test/CodeGen/Mips/eh-dwarf-cfa.ll b/llvm/test/CodeGen/Mips/eh-dwarf-cfa.ll
index 6554974..c4019c7 100644
--- a/llvm/test/CodeGen/Mips/eh-dwarf-cfa.ll
+++ b/llvm/test/CodeGen/Mips/eh-dwarf-cfa.ll
@@ -13,6 +13,8 @@
%0 = call i8* @llvm.eh.dwarf.cfa(i32 0)
ret i8* %0
+; CHECK-LABEL: f1:
+
; CHECK: addiu $sp, $sp, -32
; CHECK: addiu $2, $sp, 32
}
@@ -24,10 +26,12 @@
%0 = call i8* @llvm.eh.dwarf.cfa(i32 0)
ret i8* %0
+; CHECK-LABEL: f2:
+
; check stack size (65536 + 8)
-; CHECK: lui $[[R0:[a-z0-9]+]], 65535
-; CHECK: addiu $[[R0]], $[[R0]], -8
-; CHECK: addu $sp, $sp, $[[R0]]
+; CHECK: lui $[[R0:[a-z0-9]+]], 1
+; CHECK: addiu $[[R0]], $[[R0]], 8
+; CHECK: subu $sp, $sp, $[[R0]]
; check return value ($sp + stack size)
; CHECK: lui $[[R1:[a-z0-9]+]], 1
@@ -46,6 +50,8 @@
%add = add i32 %1, %3
ret i32 %add
+; CHECK-LABEL: f3:
+
; CHECK: addiu $sp, $sp, -40
; check return value ($fp + stack size + $fp)
@@ -60,6 +66,8 @@
%0 = call i8* @llvm.eh.dwarf.cfa(i32 0)
ret i8* %0
+; CHECK-LABEL: f4:
+
; CHECK-MIPS64: daddiu $sp, $sp, -32
; CHECK-MIPS64: daddiu $2, $sp, 32
}