This is for an experimental option -mips-os16. The idea is to compile all

Mips32 code as Mips16 unless it can't be compiled as Mips 16. For now this
would happen as long as floating point instructions are not needed.
Probably it would also make sense to compile as mips32 if atomic operations
are needed too. There may be other cases too.

A module pass prescans the IR and adds the mips16 or nomips16 attribute
to functions depending on the functions needs.

Mips 16 mode can result in a 40% code compression by utililizing 16 bit
encoding of many instructions.

The hope is for this to replace the traditional gcc way of dealing with
Mips16 code using floating point which involves essentially using soft float
but with a library implemented using mips32 floating point. This gcc 
method also requires creating stubs so that Mips32 code can interact with
these Mips 16 functions that have floating point needs. My conjecture is
that in reality this traditional gcc method would never win over this
new method.

I will be implementing the traditional gcc method also. Some of it is already
done but I needed to do the stubs to finish the work and those required
this mips16/32 mixed mode capability.

I have more ideas for to make this new method much better and I think the old
method will just live in llvm for anyone that needs the backward compatibility
but I don't for what reason that would be needed.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179185 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 149 insertions, 0 deletions

diff --git a/test/CodeGen/Mips/fpneeded.ll b/test/CodeGen/Mips/fpneeded.ll
new file mode 100644
index 0000000000..623883a0d5
--- /dev/null
+++ b/test/CodeGen/Mips/fpneeded.ll
@@ -0,0 +1,149 @@
+; RUN: llc  -march=mipsel -mcpu=mips32 -relocation-model=static -O3 < %s -mips-os16  | FileCheck %s -check-prefix=32
+
+@x = global float 1.000000e+00, align 4
+@y = global float 2.000000e+00, align 4
+@zz = common global float 0.000000e+00, align 4
+@z = common global float 0.000000e+00, align 4
+
+define float @fv() #0 {
+entry:
+  ret float 1.000000e+00
+}
+
+; 32: 	.set	nomips16                  # @fv
+; 32: 	.ent	fv
+; 32:	.set	noreorder
+; 32:	.set	nomacro
+; 32:	.set	noat
+; 32:	jr	$ra
+; 32:	.set	at
+; 32:	.set	macro
+; 32:	.set	reorder
+; 32:	.end	fv
+
+define double @dv() #0 {
+entry:
+  ret double 2.000000e+00
+}
+
+; 32: 	.set	nomips16                  # @dv
+; 32: 	.ent	dv
+; 32:	.set	noreorder
+; 32:	.set	nomacro
+; 32:	.set	noat
+; 32:	jr	$ra
+; 32:	.set	at
+; 32:	.set	macro
+; 32:	.set	reorder
+; 32:	.end	dv
+
+define void @vf(float %x) #0 {
+entry:
+  %x.addr = alloca float, align 4
+  store float %x, float* %x.addr, align 4
+  ret void
+}
+
+; 32: 	.set	nomips16                  # @vf
+; 32: 	.ent	vf
+; 32:	.set	noreorder
+; 32:	.set	nomacro
+; 32:	.set	noat
+; 32:	jr	$ra
+; 32:	.set	at
+; 32:	.set	macro
+; 32:	.set	reorder
+; 32:	.end	vf
+
+define void @vd(double %x) #0 {
+entry:
+  %x.addr = alloca double, align 8
+  store double %x, double* %x.addr, align 8
+  ret void
+}
+
+; 32: 	.set	nomips16                  # @vd
+; 32: 	.ent	vd
+; 32:	.set	noreorder
+; 32:	.set	nomacro
+; 32:	.set	noat
+; 32:	jr	$ra
+; 32:	.set	at
+; 32:	.set	macro
+; 32:	.set	reorder
+; 32:	.end	vd
+
+define void @foo1() #0 {
+entry:
+  store float 1.000000e+00, float* @zz, align 4
+  %0 = load float* @y, align 4
+  %1 = load float* @x, align 4
+  %add = fadd float %0, %1
+  store float %add, float* @z, align 4
+  ret void
+}
+
+; 32: 	.set	nomips16                  # @foo1
+; 32: 	.ent	foo1
+; 32:	.set	noreorder
+; 32:	.set	nomacro
+; 32:	.set	noat
+; 32:	jr	$ra
+; 32:	.set	at
+; 32:	.set	macro
+; 32:	.set	reorder
+; 32:	.end	foo1
+
+define void @foo2() #0 {
+entry:
+  %0 = load float* @x, align 4
+  call void @vf(float %0)
+  ret void
+}
+
+
+; 32: 	.set	nomips16                  # @foo2
+; 32: 	.ent	foo2
+; 32:	.set	noreorder
+; 32:	.set	nomacro
+; 32:	.set	noat
+; 32:	jr	$ra
+; 32:	.set	at
+; 32:	.set	macro
+; 32:	.set	reorder
+; 32:	.end	foo2
+
+define void @foo3() #0 {
+entry:
+  %call = call float @fv()
+  store float %call, float* @x, align 4
+  ret void
+}
+
+; 32: 	.set	nomips16                  # @foo3
+; 32: 	.ent	foo3
+; 32:	.set	noreorder
+; 32:	.set	nomacro
+; 32:	.set	noat
+; 32:	jr	$ra
+; 32:	.set	at
+; 32:	.set	macro
+; 32:	.set	reorder
+; 32:	.end	foo3
+
+attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+define void @vv() #0 {
+entry:
+  ret void
+}
+
+; 32: 	.set	mips16                  # @vv
+; 32: 	.ent	vv
+
+; 32:	save	{{.+}}
+; 32:	restore	{{.+}} 
+; 32:	.end	vv
+
+
+